Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

18 files changed, 3343 insertions, 0 deletions

diff --git a/image/decoders/icon/android/moz.build b/image/decoders/icon/android/moz.build
new file mode 100644
index 0000000000..a99ae228d4
--- /dev/null
+++ b/image/decoders/icon/android/moz.build
@@ -0,0 +1,13 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+SOURCES += [
+    "nsIconChannel.cpp",
+]
+
+include("/ipc/chromium/chromium-config.mozbuild")
+
+FINAL_LIBRARY = "xul"
diff --git a/image/decoders/icon/android/nsIconChannel.cpp b/image/decoders/icon/android/nsIconChannel.cpp
new file mode 100644
index 0000000000..7599cf2bb7
--- /dev/null
+++ b/image/decoders/icon/android/nsIconChannel.cpp
@@ -0,0 +1,125 @@
+/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <stdlib.h>
+#include "mozilla/gfx/Swizzle.h"
+#include "mozilla/dom/ContentChild.h"
+#include "mozilla/NullPrincipal.h"
+#include "nsMimeTypes.h"
+#include "nsXULAppAPI.h"
+#include "AndroidBridge.h"
+#include "nsIconChannel.h"
+#include "nsIIconURI.h"
+#include "nsIStringStream.h"
+#include "nsNetUtil.h"
+#include "nsComponentManagerUtils.h"
+
+NS_IMPL_ISUPPORTS(nsIconChannel, nsIRequest, nsIChannel)
+
+using namespace mozilla;
+using mozilla::dom::ContentChild;
+
+static nsresult GetIconForExtension(const nsACString& aFileExt,
+                                    uint32_t aIconSize, uint8_t* const aBuf) {
+  if (!AndroidBridge::Bridge()) {
+    return NS_ERROR_FAILURE;
+  }
+
+  AndroidBridge::Bridge()->GetIconForExtension(aFileExt, aIconSize, aBuf);
+
+  return NS_OK;
+}
+
+static nsresult CallRemoteGetIconForExtension(const nsACString& aFileExt,
+                                              uint32_t aIconSize,
+                                              uint8_t* const aBuf) {
+  NS_ENSURE_TRUE(aBuf != nullptr, NS_ERROR_NULL_POINTER);
+
+  // An array has to be used to get data from remote process
+  nsTArray<uint8_t> bits;
+  uint32_t bufSize = aIconSize * aIconSize * 4;
+
+  if (!ContentChild::GetSingleton()->SendGetIconForExtension(
+          PromiseFlatCString(aFileExt), aIconSize, &bits)) {
+    return NS_ERROR_FAILURE;
+  }
+
+  NS_ASSERTION(bits.Length() == bufSize, "Pixels array is incomplete");
+  if (bits.Length() != bufSize) {
+    return NS_ERROR_FAILURE;
+  }
+
+  memcpy(aBuf, bits.Elements(), bufSize);
+
+  return NS_OK;
+}
+
+static nsresult moz_icon_to_channel(nsIURI* aURI, const nsACString& aFileExt,
+                                    uint32_t aIconSize, nsIChannel** aChannel) {
+  NS_ENSURE_TRUE(aIconSize < 256 && aIconSize > 0, NS_ERROR_UNEXPECTED);
+
+  int width = aIconSize;
+  int height = aIconSize;
+
+  // moz-icon data should have two bytes for the size,
+  // then the ARGB pixel values with pre-multiplied Alpha
+  const int channels = 4;
+  CheckedInt32 buf_size =
+      4 + channels * CheckedInt32(height) * CheckedInt32(width);
+  if (!buf_size.isValid()) {
+    return NS_ERROR_OUT_OF_MEMORY;
+  }
+  uint8_t* const buf = (uint8_t*)moz_xmalloc(buf_size.value());
+  uint8_t* out = buf;
+
+  *(out++) = width;
+  *(out++) = height;
+  *(out++) = uint8_t(mozilla::gfx::SurfaceFormat::R8G8B8A8);
+
+  // Set all bits to ensure in nsIconDecoder we color manage and premultiply.
+  *(out++) = 0xFF;
+
+  nsresult rv;
+  if (XRE_IsParentProcess()) {
+    rv = GetIconForExtension(aFileExt, aIconSize, out);
+  } else {
+    rv = CallRemoteGetIconForExtension(aFileExt, aIconSize, out);
+  }
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsCOMPtr<nsIStringInputStream> stream =
+      do_CreateInstance("@mozilla.org/io/string-input-stream;1", &rv);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = stream->AdoptData((char*)buf, buf_size.value());
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // nsIconProtocolHandler::NewChannel will provide the correct loadInfo for
+  // this iconChannel. Use the most restrictive security settings for the
+  // temporary loadInfo to make sure the channel can not be opened.
+  nsCOMPtr<nsIPrincipal> nullPrincipal =
+      NullPrincipal::CreateWithoutOriginAttributes();
+  return NS_NewInputStreamChannel(
+      aChannel, aURI, stream.forget(), nullPrincipal,
+      nsILoadInfo::SEC_REQUIRE_SAME_ORIGIN_DATA_IS_BLOCKED,
+      nsIContentPolicy::TYPE_INTERNAL_IMAGE, nsLiteralCString(IMAGE_ICON_MS));
+}
+
+nsresult nsIconChannel::Init(nsIURI* aURI) {
+  nsCOMPtr<nsIMozIconURI> iconURI = do_QueryInterface(aURI);
+  NS_ASSERTION(iconURI, "URI is not an nsIMozIconURI");
+
+  nsAutoCString stockIcon;
+  iconURI->GetStockIcon(stockIcon);
+
+  uint32_t desiredImageSize;
+  iconURI->GetImageSize(&desiredImageSize);
+
+  nsAutoCString iconFileExt;
+  iconURI->GetFileExtension(iconFileExt);
+
+  return moz_icon_to_channel(iconURI, iconFileExt, desiredImageSize,
+                             getter_AddRefs(mRealChannel));
+}
diff --git a/image/decoders/icon/android/nsIconChannel.h b/image/decoders/icon/android/nsIconChannel.h
new file mode 100644
index 0000000000..e25196c6ee
--- /dev/null
+++ b/image/decoders/icon/android/nsIconChannel.h
@@ -0,0 +1,45 @@
+/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_image_decoders_icon_android_nsIconChannel_h
+#define mozilla_image_decoders_icon_android_nsIconChannel_h
+
+#include "mozilla/Attributes.h"
+
+#include "nsIChannel.h"
+#include "nsIURI.h"
+#include "nsCOMPtr.h"
+
+/**
+ * This class is the Android implementation of nsIconChannel.
+ * It asks Android for an icon, and creates a new channel for
+ * that file to which all calls will be proxied.
+ */
+class nsIconChannel final : public nsIChannel {
+ public:
+  NS_DECL_ISUPPORTS
+  NS_FORWARD_NSIREQUEST(mRealChannel->)
+  NS_FORWARD_NSICHANNEL(mRealChannel->)
+
+  nsIconChannel() {}
+
+  /**
+   * Called by nsIconProtocolHandler after it creates this channel.
+   * Must be called before calling any other function on this object.
+   * If this method fails, no other function must be called on this object.
+   */
+  nsresult Init(nsIURI* aURI);
+
+ private:
+  ~nsIconChannel() {}
+
+  /**
+   * The channel to the temp icon file (e.g. to /tmp/2qy9wjqw.html).
+   * Will always be non-null after a successful Init.
+   */
+  nsCOMPtr<nsIChannel> mRealChannel;
+};
+
+#endif  // mozilla_image_decoders_icon_android_nsIconChannel_h
diff --git a/image/decoders/icon/components.conf b/image/decoders/icon/components.conf
new file mode 100644
index 0000000000..68bff8e231
--- /dev/null
+++ b/image/decoders/icon/components.conf
@@ -0,0 +1,29 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+Classes = [
+    {
+        'cid': '{d0f9db12-249c-11d5-9905-001083010e9b}',
+        'contract_ids': ['@mozilla.org/network/protocol;1?name=moz-icon'],
+        'type': 'nsIconProtocolHandler',
+        'headers': ['/image/decoders/icon/nsIconProtocolHandler.h'],
+        'protocol_config': {
+            'scheme': 'moz-icon',
+            'flags': [
+                'URI_NORELATIVE',
+                'URI_NOAUTH',
+                'URI_IS_UI_RESOURCE',
+                'URI_IS_LOCAL_RESOURCE',
+            ],
+            'default_port': 0,
+        },
+    },
+    {
+        'cid': '{1460df3b-774c-4205-8349-838e507c3ef9}',
+        'type': 'nsMozIconURI::Mutator',
+        'headers': ['/image/decoders/icon/nsIconURI.h'],
+    },
+]
diff --git a/image/decoders/icon/gtk/moz.build b/image/decoders/icon/gtk/moz.build
new file mode 100644
index 0000000000..3eac86b6ba
--- /dev/null
+++ b/image/decoders/icon/gtk/moz.build
@@ -0,0 +1,20 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+SOURCES += [
+    "nsIconChannel.cpp",
+]
+
+EXPORTS += [
+    "nsIconChannel.h",
+]
+
+FINAL_LIBRARY = "xul"
+
+if CONFIG["MOZ_WIDGET_TOOLKIT"] == "gtk":
+    CXXFLAGS += CONFIG["MOZ_GTK3_CFLAGS"]
+
+include("/ipc/chromium/chromium-config.mozbuild")
diff --git a/image/decoders/icon/gtk/nsIconChannel.cpp b/image/decoders/icon/gtk/nsIconChannel.cpp
new file mode 100644
index 0000000000..2b8b958b9e
--- /dev/null
+++ b/image/decoders/icon/gtk/nsIconChannel.cpp
@@ -0,0 +1,483 @@
+/* vim:set ts=2 sw=2 sts=2 cin et: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsIconChannel.h"
+
+#include <stdlib.h>
+#include <unistd.h>
+
+#include "mozilla/DebugOnly.h"
+#include "mozilla/EndianUtils.h"
+#include "mozilla/NullPrincipal.h"
+#include "mozilla/CheckedInt.h"
+#include "mozilla/dom/ContentChild.h"
+#include "mozilla/gfx/Swizzle.h"
+#include "mozilla/ipc/ByteBuf.h"
+#include <algorithm>
+
+#include <gio/gio.h>
+
+#include <gtk/gtk.h>
+
+#include "nsMimeTypes.h"
+#include "nsIMIMEService.h"
+
+#include "nsServiceManagerUtils.h"
+
+#include "nsNetUtil.h"
+#include "nsComponentManagerUtils.h"
+#include "nsIStringStream.h"
+#include "nsServiceManagerUtils.h"
+#include "nsIURL.h"
+#include "nsIPipe.h"
+#include "nsIAsyncInputStream.h"
+#include "nsIAsyncOutputStream.h"
+#include "prlink.h"
+#include "gfxPlatform.h"
+
+using mozilla::CheckedInt32;
+using mozilla::ipc::ByteBuf;
+
+NS_IMPL_ISUPPORTS(nsIconChannel, nsIRequest, nsIChannel)
+
+static nsresult MozGdkPixbufToByteBuf(GdkPixbuf* aPixbuf, ByteBuf* aByteBuf) {
+  int width = gdk_pixbuf_get_width(aPixbuf);
+  int height = gdk_pixbuf_get_height(aPixbuf);
+  NS_ENSURE_TRUE(height < 256 && width < 256 && height > 0 && width > 0 &&
+                     gdk_pixbuf_get_colorspace(aPixbuf) == GDK_COLORSPACE_RGB &&
+                     gdk_pixbuf_get_bits_per_sample(aPixbuf) == 8 &&
+                     gdk_pixbuf_get_has_alpha(aPixbuf) &&
+                     gdk_pixbuf_get_n_channels(aPixbuf) == 4,
+                 NS_ERROR_UNEXPECTED);
+
+  const int n_channels = 4;
+  CheckedInt32 buf_size =
+      4 + n_channels * CheckedInt32(height) * CheckedInt32(width);
+  if (!buf_size.isValid()) {
+    return NS_ERROR_OUT_OF_MEMORY;
+  }
+  uint8_t* const buf = (uint8_t*)moz_xmalloc(buf_size.value());
+  uint8_t* out = buf;
+
+  *(out++) = width;
+  *(out++) = height;
+  *(out++) = uint8_t(mozilla::gfx::SurfaceFormat::OS_RGBA);
+
+  // Set all bits to ensure in nsIconDecoder we color manage and premultiply.
+  *(out++) = 0xFF;
+
+  const guchar* const pixels = gdk_pixbuf_get_pixels(aPixbuf);
+  int instride = gdk_pixbuf_get_rowstride(aPixbuf);
+  int outstride = width * n_channels;
+
+  // encode the RGB data and the A data and adjust the stride as necessary.
+  mozilla::gfx::SwizzleData(pixels, instride,
+                            mozilla::gfx::SurfaceFormat::R8G8B8A8, out,
+                            outstride, mozilla::gfx::SurfaceFormat::OS_RGBA,
+                            mozilla::gfx::IntSize(width, height));
+
+  *aByteBuf = ByteBuf(buf, buf_size.value(), buf_size.value());
+  return NS_OK;
+}
+
+static nsresult ByteBufToStream(ByteBuf&& aBuf, nsIInputStream** aStream) {
+  nsresult rv;
+  nsCOMPtr<nsIStringInputStream> stream =
+      do_CreateInstance("@mozilla.org/io/string-input-stream;1", &rv);
+
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  // stream takes ownership of buf and will free it on destruction.
+  // This function cannot fail.
+  rv = stream->AdoptData(reinterpret_cast<char*>(aBuf.mData), aBuf.mLen);
+  MOZ_ASSERT(CheckedInt32(aBuf.mLen).isValid(),
+             "aBuf.mLen should fit in int32_t");
+  aBuf.mData = nullptr;
+
+  // If this no longer holds then re-examine buf's lifetime.
+  MOZ_ASSERT(NS_SUCCEEDED(rv));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  stream.forget(aStream);
+  return NS_OK;
+}
+
+static nsresult StreamToChannel(already_AddRefed<nsIInputStream> aStream,
+                                nsIURI* aURI, nsIChannel** aChannel) {
+  // nsIconProtocolHandler::NewChannel will provide the correct loadInfo for
+  // this iconChannel. Use the most restrictive security settings for the
+  // temporary loadInfo to make sure the channel can not be opened.
+  nsCOMPtr<nsIPrincipal> nullPrincipal =
+      mozilla::NullPrincipal::CreateWithoutOriginAttributes();
+  return NS_NewInputStreamChannel(
+      aChannel, aURI, std::move(aStream), nullPrincipal,
+      nsILoadInfo::SEC_REQUIRE_SAME_ORIGIN_DATA_IS_BLOCKED,
+      nsIContentPolicy::TYPE_INTERNAL_IMAGE, nsLiteralCString(IMAGE_ICON_MS));
+}
+
+static GtkWidget* gProtoWindow = nullptr;
+static GtkWidget* gStockImageWidget = nullptr;
+
+static void ensure_stock_image_widget() {
+  // Only the style of the GtkImage needs to be used, but the widget is kept
+  // to track dynamic style changes.
+  if (!gProtoWindow) {
+    gProtoWindow = gtk_window_new(GTK_WINDOW_POPUP);
+    GtkWidget* protoLayout = gtk_fixed_new();
+    gtk_container_add(GTK_CONTAINER(gProtoWindow), protoLayout);
+
+    gStockImageWidget = gtk_image_new();
+    gtk_container_add(GTK_CONTAINER(protoLayout), gStockImageWidget);
+
+    gtk_widget_ensure_style(gStockImageWidget);
+  }
+}
+
+static GtkIconSize moz_gtk_icon_size(const char* name) {
+  if (strcmp(name, "button") == 0) {
+    return GTK_ICON_SIZE_BUTTON;
+  }
+
+  if (strcmp(name, "menu") == 0) {
+    return GTK_ICON_SIZE_MENU;
+  }
+
+  if (strcmp(name, "toolbar") == 0) {
+    return GTK_ICON_SIZE_LARGE_TOOLBAR;
+  }
+
+  if (strcmp(name, "toolbarsmall") == 0) {
+    return GTK_ICON_SIZE_SMALL_TOOLBAR;
+  }
+
+  if (strcmp(name, "dnd") == 0) {
+    return GTK_ICON_SIZE_DND;
+  }
+
+  if (strcmp(name, "dialog") == 0) {
+    return GTK_ICON_SIZE_DIALOG;
+  }
+
+  return GTK_ICON_SIZE_MENU;
+}
+
+static int32_t GetIconSize(nsIMozIconURI* aIconURI) {
+  nsAutoCString iconSizeString;
+
+  aIconURI->GetIconSize(iconSizeString);
+  if (iconSizeString.IsEmpty()) {
+    uint32_t size;
+    mozilla::DebugOnly<nsresult> rv = aIconURI->GetImageSize(&size);
+    NS_ASSERTION(NS_SUCCEEDED(rv), "GetImageSize failed");
+    return size;
+  }
+  int size;
+
+  GtkIconSize icon_size = moz_gtk_icon_size(iconSizeString.get());
+  gtk_icon_size_lookup(icon_size, &size, nullptr);
+  return size;
+}
+
+/* Scale icon buffer to preferred size */
+static nsresult ScaleIconBuf(GdkPixbuf** aBuf, int32_t iconSize) {
+  // Scale buffer only if width or height differ from preferred size
+  if (gdk_pixbuf_get_width(*aBuf) != iconSize &&
+      gdk_pixbuf_get_height(*aBuf) != iconSize) {
+    GdkPixbuf* scaled =
+        gdk_pixbuf_scale_simple(*aBuf, iconSize, iconSize, GDK_INTERP_BILINEAR);
+    // replace original buffer by scaled
+    g_object_unref(*aBuf);
+    *aBuf = scaled;
+    if (!scaled) {
+      return NS_ERROR_OUT_OF_MEMORY;
+    }
+  }
+  return NS_OK;
+}
+
+/* static */
+nsresult nsIconChannel::GetIconWithGIO(nsIMozIconURI* aIconURI,
+                                       ByteBuf* aDataOut) {
+  GIcon* icon = nullptr;
+  nsCOMPtr<nsIURL> fileURI;
+
+  // Read icon content
+  aIconURI->GetIconURL(getter_AddRefs(fileURI));
+
+  // Get icon for file specified by URI
+  if (fileURI) {
+    nsAutoCString spec;
+    fileURI->GetAsciiSpec(spec);
+    if (fileURI->SchemeIs("file")) {
+      GFile* file = g_file_new_for_uri(spec.get());
+      GFileInfo* fileInfo =
+          g_file_query_info(file, G_FILE_ATTRIBUTE_STANDARD_ICON,
+                            G_FILE_QUERY_INFO_NONE, nullptr, nullptr);
+      g_object_unref(file);
+      if (fileInfo) {
+        // icon from g_content_type_get_icon doesn't need unref
+        icon = g_file_info_get_icon(fileInfo);
+        if (icon) {
+          g_object_ref(icon);
+        }
+        g_object_unref(fileInfo);
+      }
+    }
+  }
+
+  // Try to get icon by using MIME type
+  if (!icon) {
+    nsAutoCString type;
+    aIconURI->GetContentType(type);
+    // Try to get MIME type from file extension by using nsIMIMEService
+    if (type.IsEmpty()) {
+      nsCOMPtr<nsIMIMEService> ms(do_GetService("@mozilla.org/mime;1"));
+      if (ms) {
+        nsAutoCString fileExt;
+        aIconURI->GetFileExtension(fileExt);
+        ms->GetTypeFromExtension(fileExt, type);
+      }
+    }
+    char* ctype = nullptr;  // character representation of content type
+    if (!type.IsEmpty()) {
+      ctype = g_content_type_from_mime_type(type.get());
+    }
+    if (ctype) {
+      icon = g_content_type_get_icon(ctype);
+      g_free(ctype);
+    }
+  }
+
+  // Get default icon theme
+  GtkIconTheme* iconTheme = gtk_icon_theme_get_default();
+  GtkIconInfo* iconInfo = nullptr;
+  // Get icon size
+  int32_t iconSize = GetIconSize(aIconURI);
+
+  if (icon) {
+    // Use icon and theme to get GtkIconInfo
+    iconInfo = gtk_icon_theme_lookup_by_gicon(iconTheme, icon, iconSize,
+                                              (GtkIconLookupFlags)0);
+    g_object_unref(icon);
+  }
+
+  if (!iconInfo) {
+    // Mozilla's mimetype lookup failed. Try the "unknown" icon.
+    iconInfo = gtk_icon_theme_lookup_icon(iconTheme, "unknown", iconSize,
+                                          (GtkIconLookupFlags)0);
+    if (!iconInfo) {
+      return NS_ERROR_NOT_AVAILABLE;
+    }
+  }
+
+  // Create a GdkPixbuf buffer containing icon and scale it
+  GdkPixbuf* buf = gtk_icon_info_load_icon(iconInfo, nullptr);
+  gtk_icon_info_free(iconInfo);
+  if (!buf) {
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  nsresult rv = ScaleIconBuf(&buf, iconSize);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = MozGdkPixbufToByteBuf(buf, aDataOut);
+  g_object_unref(buf);
+  return rv;
+}
+
+/* static */
+nsresult nsIconChannel::GetIcon(nsIURI* aURI, ByteBuf* aDataOut) {
+  nsCOMPtr<nsIMozIconURI> iconURI = do_QueryInterface(aURI);
+  NS_ASSERTION(iconURI, "URI is not an nsIMozIconURI");
+
+  if (!iconURI) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  if (gfxPlatform::IsHeadless()) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  nsAutoCString stockIcon;
+  iconURI->GetStockIcon(stockIcon);
+  if (stockIcon.IsEmpty()) {
+    return GetIconWithGIO(iconURI, aDataOut);
+  }
+
+  // Search for stockIcon
+  nsAutoCString iconSizeString;
+  iconURI->GetIconSize(iconSizeString);
+
+  nsAutoCString iconStateString;
+  iconURI->GetIconState(iconStateString);
+
+  GtkIconSize icon_size = moz_gtk_icon_size(iconSizeString.get());
+  GtkStateType state = iconStateString.EqualsLiteral("disabled")
+                           ? GTK_STATE_INSENSITIVE
+                           : GTK_STATE_NORMAL;
+
+  // First lookup the icon by stock id and text direction.
+  GtkTextDirection direction = GTK_TEXT_DIR_NONE;
+  if (StringEndsWith(stockIcon, "-ltr"_ns)) {
+    direction = GTK_TEXT_DIR_LTR;
+  } else if (StringEndsWith(stockIcon, "-rtl"_ns)) {
+    direction = GTK_TEXT_DIR_RTL;
+  }
+
+  bool forceDirection = direction != GTK_TEXT_DIR_NONE;
+  nsAutoCString stockID;
+  bool useIconName = false;
+  if (!forceDirection) {
+    direction = gtk_widget_get_default_direction();
+    stockID = stockIcon;
+  } else {
+    // GTK versions < 2.22 use icon names from concatenating stock id with
+    // -(rtl|ltr), which is how the moz-icon stock name is interpreted here.
+    stockID = Substring(stockIcon, 0, stockIcon.Length() - 4);
+    // However, if we lookup bidi icons by the stock name, then GTK versions
+    // >= 2.22 will use a bidi lookup convention that most icon themes do not
+    // yet follow.  Therefore, we first check to see if the theme supports the
+    // old icon name as this will have bidi support (if found).
+    GtkIconTheme* icon_theme = gtk_icon_theme_get_default();
+    // Micking what gtk_icon_set_render_icon does with sizes, though it's not
+    // critical as icons will be scaled to suit size.  It just means we follow
+    // the same paths and so share caches.
+    gint width, height;
+    if (gtk_icon_size_lookup(icon_size, &width, &height)) {
+      gint size = std::min(width, height);
+      // We use gtk_icon_theme_lookup_icon() without
+      // GTK_ICON_LOOKUP_USE_BUILTIN instead of gtk_icon_theme_has_icon() so
+      // we don't pick up fallback icons added by distributions for backward
+      // compatibility.
+      GtkIconInfo* icon = gtk_icon_theme_lookup_icon(
+          icon_theme, stockIcon.get(), size, (GtkIconLookupFlags)0);
+      if (icon) {
+        useIconName = true;
+        gtk_icon_info_free(icon);
+      }
+    }
+  }
+
+  ensure_stock_image_widget();
+  GtkStyle* style = gtk_widget_get_style(gStockImageWidget);
+  GtkIconSet* icon_set = nullptr;
+  if (!useIconName) {
+    icon_set = gtk_style_lookup_icon_set(style, stockID.get());
+  }
+
+  if (!icon_set) {
+    // Either we have chosen icon-name lookup for a bidi icon, or stockIcon is
+    // not a stock id so we assume it is an icon name.
+    useIconName = true;
+    // Creating a GtkIconSet is a convenient way to allow the style to
+    // render the icon, possibly with variations suitable for insensitive
+    // states.
+    icon_set = gtk_icon_set_new();
+    GtkIconSource* icon_source = gtk_icon_source_new();
+
+    gtk_icon_source_set_icon_name(icon_source, stockIcon.get());
+    gtk_icon_set_add_source(icon_set, icon_source);
+    gtk_icon_source_free(icon_source);
+  }
+
+  GdkPixbuf* icon = gtk_icon_set_render_icon(
+      icon_set, style, direction, state, icon_size, gStockImageWidget, nullptr);
+  if (useIconName) {
+    gtk_icon_set_unref(icon_set);
+  }
+
+  // According to documentation, gtk_icon_set_render_icon() never returns
+  // nullptr, but it does return nullptr when we have the problem reported
+  // here: https://bugzilla.gnome.org/show_bug.cgi?id=629878#c13
+  if (!icon) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  nsresult rv = MozGdkPixbufToByteBuf(icon, aDataOut);
+
+  g_object_unref(icon);
+
+  return rv;
+}
+
+nsresult nsIconChannel::Init(nsIURI* aURI) {
+  nsCOMPtr<nsIInputStream> stream;
+
+  using ContentChild = mozilla::dom::ContentChild;
+  if (auto* contentChild = ContentChild::GetSingleton()) {
+    // Get the icon via IPC and translate the promise of a ByteBuf
+    // into an actually-existing channel.
+    RefPtr<ContentChild::GetSystemIconPromise> icon =
+        contentChild->SendGetSystemIcon(aURI);
+    if (!icon) {
+      return NS_ERROR_UNEXPECTED;
+    }
+
+    nsCOMPtr<nsIAsyncInputStream> inputStream;
+    nsCOMPtr<nsIAsyncOutputStream> outputStream;
+    NS_NewPipe2(getter_AddRefs(inputStream), getter_AddRefs(outputStream), true,
+                false, 0, UINT32_MAX);
+
+    // FIXME: Bug 1718324
+    // The GetSystemIcon() call will end up on the parent doing GetIcon()
+    // and by using ByteBuf we might not be immune to some deadlock, at least
+    // on paper. From analysis in
+    // https://phabricator.services.mozilla.com/D118596#3865440 we should be
+    // safe in practice, but it would be nicer to just write that differently.
+
+    icon->Then(
+        mozilla::GetCurrentSerialEventTarget(), __func__,
+        [outputStream](std::tuple<nsresult, mozilla::Maybe<ByteBuf>>&& aArg) {
+          nsresult rv = std::get<0>(aArg);
+          mozilla::Maybe<ByteBuf> bytes = std::move(std::get<1>(aArg));
+
+          if (NS_SUCCEEDED(rv)) {
+            MOZ_RELEASE_ASSERT(bytes);
+            uint32_t written;
+            rv = outputStream->Write(reinterpret_cast<char*>(bytes->mData),
+                                     static_cast<uint32_t>(bytes->mLen),
+                                     &written);
+            if (NS_SUCCEEDED(rv)) {
+              const bool wroteAll = static_cast<size_t>(written) == bytes->mLen;
+              MOZ_ASSERT(wroteAll);
+              if (!wroteAll) {
+                rv = NS_ERROR_UNEXPECTED;
+              }
+            }
+          } else {
+            MOZ_ASSERT(!bytes);
+          }
+
+          if (NS_FAILED(rv)) {
+            outputStream->CloseWithStatus(rv);
+          }
+        },
+        [outputStream](mozilla::ipc::ResponseRejectReason) {
+          outputStream->CloseWithStatus(NS_ERROR_FAILURE);
+        });
+
+    stream = inputStream.forget();
+  } else {
+    // Get the icon directly.
+    ByteBuf bytebuf;
+    nsresult rv = GetIcon(aURI, &bytebuf);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    rv = ByteBufToStream(std::move(bytebuf), getter_AddRefs(stream));
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  return StreamToChannel(stream.forget(), aURI, getter_AddRefs(mRealChannel));
+}
+
+void nsIconChannel::Shutdown() {
+  if (gProtoWindow) {
+    gtk_widget_destroy(gProtoWindow);
+    gProtoWindow = nullptr;
+    gStockImageWidget = nullptr;
+  }
+}
diff --git a/image/decoders/icon/gtk/nsIconChannel.h b/image/decoders/icon/gtk/nsIconChannel.h
new file mode 100644
index 0000000000..6ad26602d0
--- /dev/null
+++ b/image/decoders/icon/gtk/nsIconChannel.h
@@ -0,0 +1,53 @@
+/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_image_decoders_icon_gtk_nsIconChannel_h
+#define mozilla_image_decoders_icon_gtk_nsIconChannel_h
+
+#include "mozilla/Attributes.h"
+
+#include "nsIChannel.h"
+#include "nsIURI.h"
+#include "nsIIconURI.h"
+#include "nsCOMPtr.h"
+
+namespace mozilla::ipc {
+class ByteBuf;
+}
+
+/// This class is the GTK implementation of nsIconChannel.  It asks
+/// GTK for the icon, translates the pixel data in-memory into
+/// nsIconDecoder format, and proxies the nsChannel interface to a new
+/// channel returning that image.
+class nsIconChannel final : public nsIChannel {
+ public:
+  NS_DECL_ISUPPORTS
+  NS_FORWARD_NSIREQUEST(mRealChannel->)
+  NS_FORWARD_NSICHANNEL(mRealChannel->)
+
+  nsIconChannel() {}
+
+  static void Shutdown();
+
+  /// Called by nsIconProtocolHandler after it creates this channel.
+  /// Must be called before calling any other function on this object.
+  /// If this method fails, no other function must be called on this object.
+  nsresult Init(nsIURI* aURI);
+
+  /// Obtains an icon, in nsIconDecoder format, as a ByteBuf instead
+  /// of a channel.  For use with IPC.
+  static nsresult GetIcon(nsIURI* aURI, mozilla::ipc::ByteBuf* aDataOut);
+
+ private:
+  ~nsIconChannel() {}
+  /// The input stream channel which will yield the image.
+  /// Will always be non-null after a successful Init.
+  nsCOMPtr<nsIChannel> mRealChannel;
+
+  static nsresult GetIconWithGIO(nsIMozIconURI* aIconURI,
+                                 mozilla::ipc::ByteBuf* aDataOut);
+};
+
+#endif  // mozilla_image_decoders_icon_gtk_nsIconChannel_h
diff --git a/image/decoders/icon/mac/moz.build b/image/decoders/icon/mac/moz.build
new file mode 100644
index 0000000000..3467659a8f
--- /dev/null
+++ b/image/decoders/icon/mac/moz.build
@@ -0,0 +1,13 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+SOURCES += [
+    "nsIconChannelCocoa.mm",
+]
+
+FINAL_LIBRARY = "xul"
+
+include("/ipc/chromium/chromium-config.mozbuild")
diff --git a/image/decoders/icon/mac/nsIconChannel.h b/image/decoders/icon/mac/nsIconChannel.h
new file mode 100644
index 0000000000..dca2a3c51a
--- /dev/null
+++ b/image/decoders/icon/mac/nsIconChannel.h
@@ -0,0 +1,61 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_image_encoders_icon_mac_nsIconChannel_h
+#define mozilla_image_encoders_icon_mac_nsIconChannel_h
+
+#include "mozilla/Attributes.h"
+
+#include "nsCOMPtr.h"
+#include "nsString.h"
+#include "nsIChannel.h"
+#include "nsILoadGroup.h"
+#include "nsILoadInfo.h"
+#include "nsIInterfaceRequestor.h"
+#include "nsIInterfaceRequestorUtils.h"
+#include "nsIInputStreamPump.h"
+#include "nsIStreamListener.h"
+#include "nsIURI.h"
+#include "nsNetUtil.h"
+
+class nsIFile;
+
+class nsIconChannel final : public nsIChannel, public nsIStreamListener {
+ public:
+  NS_DECL_THREADSAFE_ISUPPORTS
+  NS_DECL_NSIREQUEST
+  NS_DECL_NSICHANNEL
+  NS_DECL_NSIREQUESTOBSERVER
+  NS_DECL_NSISTREAMLISTENER
+
+  nsIconChannel();
+
+  nsresult Init(nsIURI* uri);
+
+ protected:
+  virtual ~nsIconChannel();
+
+  nsCOMPtr<nsIURI> mUrl;
+  nsCOMPtr<nsIURI> mOriginalURI;
+  nsCOMPtr<nsILoadGroup> mLoadGroup;
+  nsCOMPtr<nsIInterfaceRequestor> mCallbacks;
+  nsCOMPtr<nsISupports> mOwner;
+  nsCOMPtr<nsILoadInfo> mLoadInfo;
+
+  nsCOMPtr<nsIInputStreamPump> mPump;
+  nsCOMPtr<nsIStreamListener> mListener;
+  bool mCanceled = false;
+
+  [[nodiscard]] nsresult MakeInputStream(nsIInputStream** _retval,
+                                         bool nonBlocking);
+
+  nsresult ExtractIconInfoFromUrl(nsIFile** aLocalFile,
+                                  uint32_t* aDesiredImageSize,
+                                  nsACString& aContentType,
+                                  nsACString& aFileExtension);
+};
+
+#endif  // mozilla_image_encoders_icon_mac_nsIconChannel_h
diff --git a/image/decoders/icon/mac/nsIconChannelCocoa.mm b/image/decoders/icon/mac/nsIconChannelCocoa.mm
new file mode 100644
index 0000000000..368ecdda20
--- /dev/null
+++ b/image/decoders/icon/mac/nsIconChannelCocoa.mm
@@ -0,0 +1,505 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsContentUtils.h"
+#include "nsIconChannel.h"
+#include "mozilla/BasePrincipal.h"
+#include "mozilla/EndianUtils.h"
+#include "nsComponentManagerUtils.h"
+#include "nsIIconURI.h"
+#include "nsIInputStream.h"
+#include "nsIInterfaceRequestor.h"
+#include "nsIInterfaceRequestorUtils.h"
+#include "nsString.h"
+#include "nsMimeTypes.h"
+#include "nsIURL.h"
+#include "nsNetCID.h"
+#include "nsIPipe.h"
+#include "nsIOutputStream.h"
+#include "nsCExternalHandlerService.h"
+#include "nsILocalFileMac.h"
+#include "nsIFileURL.h"
+#include "nsTArray.h"
+#include "nsObjCExceptions.h"
+#include "nsProxyRelease.h"
+#include "nsContentSecurityManager.h"
+#include "nsNetUtil.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/UniquePtrExtensions.h"
+
+#include <Cocoa/Cocoa.h>
+
+using namespace mozilla;
+
+// nsIconChannel methods
+nsIconChannel::nsIconChannel() {}
+
+nsIconChannel::~nsIconChannel() {
+  if (mLoadInfo) {
+    NS_ReleaseOnMainThread("nsIconChannel::mLoadInfo", mLoadInfo.forget());
+  }
+}
+
+NS_IMPL_ISUPPORTS(nsIconChannel, nsIChannel, nsIRequest, nsIRequestObserver, nsIStreamListener)
+
+nsresult nsIconChannel::Init(nsIURI* uri) {
+  NS_ASSERTION(uri, "no uri");
+  mUrl = uri;
+  mOriginalURI = uri;
+  nsresult rv;
+  mPump = do_CreateInstance(NS_INPUTSTREAMPUMP_CONTRACTID, &rv);
+  return rv;
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// nsIRequest methods:
+
+NS_IMETHODIMP
+nsIconChannel::GetName(nsACString& result) { return mUrl->GetSpec(result); }
+
+NS_IMETHODIMP
+nsIconChannel::IsPending(bool* result) { return mPump->IsPending(result); }
+
+NS_IMETHODIMP
+nsIconChannel::GetStatus(nsresult* status) { return mPump->GetStatus(status); }
+
+NS_IMETHODIMP nsIconChannel::SetCanceledReason(const nsACString& aReason) {
+  return SetCanceledReasonImpl(aReason);
+}
+
+NS_IMETHODIMP nsIconChannel::GetCanceledReason(nsACString& aReason) {
+  return GetCanceledReasonImpl(aReason);
+}
+
+NS_IMETHODIMP nsIconChannel::CancelWithReason(nsresult aStatus, const nsACString& aReason) {
+  return CancelWithReasonImpl(aStatus, aReason);
+}
+
+NS_IMETHODIMP
+nsIconChannel::Cancel(nsresult status) {
+  mCanceled = true;
+  return mPump->Cancel(status);
+}
+
+NS_IMETHODIMP
+nsIconChannel::GetCanceled(bool* result) {
+  *result = mCanceled;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsIconChannel::Suspend(void) { return mPump->Suspend(); }
+
+NS_IMETHODIMP
+nsIconChannel::Resume(void) { return mPump->Resume(); }
+
+// nsIRequestObserver methods
+NS_IMETHODIMP
+nsIconChannel::OnStartRequest(nsIRequest* aRequest) {
+  if (mListener) {
+    return mListener->OnStartRequest(this);
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsIconChannel::OnStopRequest(nsIRequest* aRequest, nsresult aStatus) {
+  if (mListener) {
+    mListener->OnStopRequest(this, aStatus);
+    mListener = nullptr;
+  }
+
+  // Remove from load group
+  if (mLoadGroup) {
+    mLoadGroup->RemoveRequest(this, nullptr, aStatus);
+  }
+
+  return NS_OK;
+}
+
+// nsIStreamListener methods
+NS_IMETHODIMP
+nsIconChannel::OnDataAvailable(nsIRequest* aRequest, nsIInputStream* aStream, uint64_t aOffset,
+                               uint32_t aCount) {
+  if (mListener) {
+    return mListener->OnDataAvailable(this, aStream, aOffset, aCount);
+  }
+  return NS_OK;
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// nsIChannel methods:
+
+NS_IMETHODIMP
+nsIconChannel::GetOriginalURI(nsIURI** aURI) {
+  *aURI = mOriginalURI;
+  NS_ADDREF(*aURI);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsIconChannel::SetOriginalURI(nsIURI* aURI) {
+  NS_ENSURE_ARG_POINTER(aURI);
+  mOriginalURI = aURI;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsIconChannel::GetURI(nsIURI** aURI) {
+  *aURI = mUrl;
+  NS_IF_ADDREF(*aURI);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsIconChannel::Open(nsIInputStream** _retval) {
+  nsCOMPtr<nsIStreamListener> listener;
+  nsresult rv = nsContentSecurityManager::doContentSecurityCheck(this, listener);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  return MakeInputStream(_retval, false);
+}
+
+nsresult nsIconChannel::ExtractIconInfoFromUrl(nsIFile** aLocalFile, uint32_t* aDesiredImageSize,
+                                               nsACString& aContentType,
+                                               nsACString& aFileExtension) {
+  nsresult rv = NS_OK;
+  nsCOMPtr<nsIMozIconURI> iconURI(do_QueryInterface(mUrl, &rv));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  iconURI->GetImageSize(aDesiredImageSize);
+  iconURI->GetContentType(aContentType);
+  iconURI->GetFileExtension(aFileExtension);
+
+  nsCOMPtr<nsIURL> url;
+  rv = iconURI->GetIconURL(getter_AddRefs(url));
+  if (NS_FAILED(rv) || !url) return NS_OK;
+
+  nsCOMPtr<nsIFileURL> fileURL = do_QueryInterface(url, &rv);
+  if (NS_FAILED(rv) || !fileURL) return NS_OK;
+
+  nsCOMPtr<nsIFile> file;
+  rv = fileURL->GetFile(getter_AddRefs(file));
+  if (NS_FAILED(rv) || !file) return NS_OK;
+
+  nsCOMPtr<nsILocalFileMac> localFileMac(do_QueryInterface(file, &rv));
+  if (NS_FAILED(rv) || !localFileMac) return NS_OK;
+
+  *aLocalFile = file;
+  NS_IF_ADDREF(*aLocalFile);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsIconChannel::AsyncOpen(nsIStreamListener* aListener) {
+  nsCOMPtr<nsIStreamListener> listener = aListener;
+  nsresult rv = nsContentSecurityManager::doContentSecurityCheck(this, listener);
+  if (NS_FAILED(rv)) {
+    mCallbacks = nullptr;
+    return rv;
+  }
+
+  MOZ_ASSERT(mLoadInfo->GetSecurityMode() == 0 || mLoadInfo->GetInitialSecurityCheckDone() ||
+                 (mLoadInfo->GetSecurityMode() ==
+                      nsILoadInfo::SEC_ALLOW_CROSS_ORIGIN_SEC_CONTEXT_IS_NULL &&
+                  mLoadInfo->GetLoadingPrincipal() &&
+                  mLoadInfo->GetLoadingPrincipal()->IsSystemPrincipal()),
+             "security flags in loadInfo but doContentSecurityCheck() not called");
+
+  nsCOMPtr<nsIInputStream> inStream;
+  rv = MakeInputStream(getter_AddRefs(inStream), true);
+  if (NS_FAILED(rv)) {
+    mCallbacks = nullptr;
+    return rv;
+  }
+
+  // Init our stream pump
+  nsCOMPtr<nsISerialEventTarget> target =
+      nsContentUtils::GetEventTargetByLoadInfo(mLoadInfo, mozilla::TaskCategory::Other);
+  rv = mPump->Init(inStream, 0, 0, false, target);
+  if (NS_FAILED(rv)) {
+    mCallbacks = nullptr;
+    return rv;
+  }
+
+  rv = mPump->AsyncRead(this);
+  if (NS_SUCCEEDED(rv)) {
+    // Store our real listener
+    mListener = aListener;
+    // Add ourself to the load group, if available
+    if (mLoadGroup) {
+      mLoadGroup->AddRequest(this, nullptr);
+    }
+  } else {
+    mCallbacks = nullptr;
+  }
+
+  return rv;
+}
+
+nsresult nsIconChannel::MakeInputStream(nsIInputStream** _retval, bool aNonBlocking) {
+  NS_OBJC_BEGIN_TRY_BLOCK_RETURN;
+
+  nsCString contentType;
+  nsAutoCString fileExt;
+  nsCOMPtr<nsIFile> fileloc;  // file we want an icon for
+  uint32_t desiredImageSize;
+  nsresult rv =
+      ExtractIconInfoFromUrl(getter_AddRefs(fileloc), &desiredImageSize, contentType, fileExt);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  bool fileExists = false;
+  if (fileloc) {
+    fileloc->Exists(&fileExists);
+  }
+
+  NSImage* iconImage = nil;
+
+  // first try to get the icon from the file if it exists
+  if (fileExists) {
+    nsCOMPtr<nsILocalFileMac> localFileMac(do_QueryInterface(fileloc, &rv));
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    CFURLRef macURL;
+    if (NS_SUCCEEDED(localFileMac->GetCFURL(&macURL))) {
+      iconImage = [[NSWorkspace sharedWorkspace] iconForFile:[(NSURL*)macURL path]];
+      ::CFRelease(macURL);
+    }
+  }
+
+  // if we don't have an icon yet try to get one by extension
+  if (!iconImage && !fileExt.IsEmpty()) {
+    NSString* fileExtension = [NSString stringWithUTF8String:fileExt.get()];
+    iconImage = [[NSWorkspace sharedWorkspace] iconForFileType:fileExtension];
+  }
+
+  // If we still don't have an icon, get the generic document icon.
+  if (!iconImage) {
+    iconImage = [[NSWorkspace sharedWorkspace] iconForFileType:NSFileTypeUnknown];
+  }
+
+  if (!iconImage) {
+    return NS_ERROR_FAILURE;
+  }
+
+  if (desiredImageSize > 255) {
+    // The Icon image format represents width and height as u8, so it does not
+    // allow for images sized 256 or more.
+    return NS_ERROR_FAILURE;
+  }
+
+  // Set the actual size to *twice* the requested size.
+  // We do this because our UI doesn't take the window's device pixel ratio into
+  // account when it requests these icons; e.g. it will request an icon with
+  // size 16, place it in a 16x16 CSS pixel sized image, and then display it in
+  // a window on a HiDPI screen where the icon now covers 32x32 physical screen
+  // pixels. So we just always double the size here in order to prevent blurriness.
+  uint32_t size = (desiredImageSize < 128) ? desiredImageSize * 2 : desiredImageSize;
+  uint32_t width = size;
+  uint32_t height = size;
+
+  // The "image format" we're outputting here (and which gets decoded by
+  // nsIconDecoder) has the following format:
+  //  - 1 byte for the image width, as u8
+  //  - 1 byte for the image height, as u8
+  //  - the raw image data as BGRA, width * height * 4 bytes.
+  size_t bufferCapacity = 4 + width * height * 4;
+  UniquePtr<uint8_t[]> fileBuf = MakeUniqueFallible<uint8_t[]>(bufferCapacity);
+  if (NS_WARN_IF(!fileBuf)) {
+    return NS_ERROR_OUT_OF_MEMORY;
+  }
+
+  fileBuf[0] = uint8_t(width);
+  fileBuf[1] = uint8_t(height);
+  fileBuf[2] = uint8_t(mozilla::gfx::SurfaceFormat::B8G8R8A8);
+
+  // Clear all bits to ensure in nsIconDecoder we assume we are already color
+  // managed and premultiplied.
+  fileBuf[3] = 0;
+
+  uint8_t* imageBuf = &fileBuf[4];
+
+  // Create a CGBitmapContext around imageBuf and draw iconImage to it.
+  // This gives us the image data in the format we want: BGRA, four bytes per
+  // pixel, in host endianness, with premultiplied alpha.
+  CGColorSpaceRef cs = CGColorSpaceCreateDeviceRGB();
+  CGContextRef ctx =
+      CGBitmapContextCreate(imageBuf, width, height, 8 /* bitsPerComponent */, width * 4, cs,
+                            kCGBitmapByteOrder32Host | kCGImageAlphaPremultipliedFirst);
+  CGColorSpaceRelease(cs);
+
+  NSGraphicsContext* oldContext = [NSGraphicsContext currentContext];
+  [NSGraphicsContext setCurrentContext:[NSGraphicsContext graphicsContextWithCGContext:ctx
+                                                                               flipped:NO]];
+
+  [iconImage drawInRect:NSMakeRect(0, 0, width, height)];
+
+  [NSGraphicsContext setCurrentContext:oldContext];
+
+  CGContextRelease(ctx);
+
+  // Now, create a pipe and stuff our data into it
+  nsCOMPtr<nsIInputStream> inStream;
+  nsCOMPtr<nsIOutputStream> outStream;
+  NS_NewPipe(getter_AddRefs(inStream), getter_AddRefs(outStream), bufferCapacity, bufferCapacity,
+             aNonBlocking);
+
+  uint32_t written;
+  rv = outStream->Write((char*)fileBuf.get(), bufferCapacity, &written);
+  if (NS_SUCCEEDED(rv)) {
+    NS_IF_ADDREF(*_retval = inStream);
+  }
+
+  // Drop notification callbacks to prevent cycles.
+  mCallbacks = nullptr;
+
+  return NS_OK;
+
+  NS_OBJC_END_TRY_BLOCK_RETURN(NS_ERROR_FAILURE);
+}
+
+NS_IMETHODIMP
+nsIconChannel::GetLoadFlags(uint32_t* aLoadAttributes) {
+  return mPump->GetLoadFlags(aLoadAttributes);
+}
+
+NS_IMETHODIMP
+nsIconChannel::SetLoadFlags(uint32_t aLoadAttributes) {
+  return mPump->SetLoadFlags(aLoadAttributes);
+}
+
+NS_IMETHODIMP
+nsIconChannel::GetTRRMode(nsIRequest::TRRMode* aTRRMode) { return GetTRRModeImpl(aTRRMode); }
+
+NS_IMETHODIMP
+nsIconChannel::SetTRRMode(nsIRequest::TRRMode aTRRMode) { return SetTRRModeImpl(aTRRMode); }
+
+NS_IMETHODIMP
+nsIconChannel::GetIsDocument(bool* aIsDocument) {
+  return NS_GetIsDocumentChannel(this, aIsDocument);
+}
+
+NS_IMETHODIMP
+nsIconChannel::GetContentType(nsACString& aContentType) {
+  aContentType.AssignLiteral(IMAGE_ICON_MS);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsIconChannel::SetContentType(const nsACString& aContentType) {
+  // It doesn't make sense to set the content-type on this type
+  // of channel...
+  return NS_ERROR_FAILURE;
+}
+
+NS_IMETHODIMP
+nsIconChannel::GetContentCharset(nsACString& aContentCharset) {
+  aContentCharset.AssignLiteral(IMAGE_ICON_MS);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsIconChannel::SetContentCharset(const nsACString& aContentCharset) {
+  // It doesn't make sense to set the content-type on this type
+  // of channel...
+  return NS_ERROR_FAILURE;
+}
+
+NS_IMETHODIMP
+nsIconChannel::GetContentDisposition(uint32_t* aContentDisposition) {
+  return NS_ERROR_NOT_AVAILABLE;
+}
+
+NS_IMETHODIMP
+nsIconChannel::SetContentDisposition(uint32_t aContentDisposition) {
+  return NS_ERROR_NOT_AVAILABLE;
+}
+
+NS_IMETHODIMP
+nsIconChannel::GetContentDispositionFilename(nsAString& aContentDispositionFilename) {
+  return NS_ERROR_NOT_AVAILABLE;
+}
+
+NS_IMETHODIMP
+nsIconChannel::SetContentDispositionFilename(const nsAString& aContentDispositionFilename) {
+  return NS_ERROR_NOT_AVAILABLE;
+}
+
+NS_IMETHODIMP
+nsIconChannel::GetContentDispositionHeader(nsACString& aContentDispositionHeader) {
+  return NS_ERROR_NOT_AVAILABLE;
+}
+
+NS_IMETHODIMP
+nsIconChannel::GetContentLength(int64_t* aContentLength) {
+  *aContentLength = 0;
+  return NS_ERROR_FAILURE;
+}
+
+NS_IMETHODIMP
+nsIconChannel::SetContentLength(int64_t aContentLength) {
+  MOZ_ASSERT_UNREACHABLE("nsIconChannel::SetContentLength");
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+nsIconChannel::GetLoadGroup(nsILoadGroup** aLoadGroup) {
+  *aLoadGroup = mLoadGroup;
+  NS_IF_ADDREF(*aLoadGroup);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsIconChannel::SetLoadGroup(nsILoadGroup* aLoadGroup) {
+  mLoadGroup = aLoadGroup;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsIconChannel::GetOwner(nsISupports** aOwner) {
+  *aOwner = mOwner.get();
+  NS_IF_ADDREF(*aOwner);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsIconChannel::SetOwner(nsISupports* aOwner) {
+  mOwner = aOwner;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsIconChannel::GetLoadInfo(nsILoadInfo** aLoadInfo) {
+  NS_IF_ADDREF(*aLoadInfo = mLoadInfo);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsIconChannel::SetLoadInfo(nsILoadInfo* aLoadInfo) {
+  MOZ_RELEASE_ASSERT(aLoadInfo, "loadinfo can't be null");
+  mLoadInfo = aLoadInfo;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsIconChannel::GetNotificationCallbacks(nsIInterfaceRequestor** aNotificationCallbacks) {
+  *aNotificationCallbacks = mCallbacks.get();
+  NS_IF_ADDREF(*aNotificationCallbacks);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsIconChannel::SetNotificationCallbacks(nsIInterfaceRequestor* aNotificationCallbacks) {
+  mCallbacks = aNotificationCallbacks;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsIconChannel::GetSecurityInfo(nsITransportSecurityInfo** aSecurityInfo) {
+  *aSecurityInfo = nullptr;
+  return NS_OK;
+}
diff --git a/image/decoders/icon/moz.build b/image/decoders/icon/moz.build
new file mode 100644
index 0000000000..96cf951b3b
--- /dev/null
+++ b/image/decoders/icon/moz.build
@@ -0,0 +1,39 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+UNIFIED_SOURCES += [
+    "nsIconProtocolHandler.cpp",
+    "nsIconURI.cpp",
+]
+
+XPCOM_MANIFESTS += [
+    "components.conf",
+]
+
+FINAL_LIBRARY = "xul"
+
+include("/ipc/chromium/chromium-config.mozbuild")
+
+EXPORTS += [
+    "nsIconURI.h",
+]
+
+platform = None
+
+if CONFIG["MOZ_WIDGET_TOOLKIT"] == "gtk":
+    platform = "gtk"
+
+if CONFIG["OS_ARCH"] == "WINNT":
+    platform = "win"
+
+if CONFIG["MOZ_WIDGET_TOOLKIT"] == "cocoa":
+    platform = "mac"
+
+if CONFIG["OS_TARGET"] == "Android":
+    platform = "android"
+
+if platform:
+    LOCAL_INCLUDES += [platform]
diff --git a/image/decoders/icon/nsIconProtocolHandler.cpp b/image/decoders/icon/nsIconProtocolHandler.cpp
new file mode 100644
index 0000000000..9334f908db
--- /dev/null
+++ b/image/decoders/icon/nsIconProtocolHandler.cpp
@@ -0,0 +1,68 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsIconProtocolHandler.h"
+
+#include "nsIconChannel.h"
+#include "nsIconURI.h"
+#include "nsCRT.h"
+#include "nsCOMPtr.h"
+#include "nsNetCID.h"
+
+///////////////////////////////////////////////////////////////////////////////
+
+nsIconProtocolHandler::nsIconProtocolHandler() {}
+
+nsIconProtocolHandler::~nsIconProtocolHandler() {}
+
+NS_IMPL_ISUPPORTS(nsIconProtocolHandler, nsIProtocolHandler,
+                  nsISupportsWeakReference)
+
+///////////////////////////////////////////////////////////////////////////////
+// nsIProtocolHandler methods:
+
+NS_IMETHODIMP
+nsIconProtocolHandler::GetScheme(nsACString& result) {
+  result = "moz-icon";
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsIconProtocolHandler::AllowPort(int32_t port, const char* scheme,
+                                 bool* _retval) {
+  // don't override anything.
+  *_retval = false;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsIconProtocolHandler::NewChannel(nsIURI* url, nsILoadInfo* aLoadInfo,
+                                  nsIChannel** result) {
+  NS_ENSURE_ARG_POINTER(url);
+  nsIconChannel* channel = new nsIconChannel;
+  if (!channel) {
+    return NS_ERROR_OUT_OF_MEMORY;
+  }
+  NS_ADDREF(channel);
+
+  nsresult rv = channel->Init(url);
+  if (NS_FAILED(rv)) {
+    NS_RELEASE(channel);
+    return rv;
+  }
+
+  // set the loadInfo on the new channel
+  rv = channel->SetLoadInfo(aLoadInfo);
+  if (NS_FAILED(rv)) {
+    NS_RELEASE(channel);
+    return rv;
+  }
+
+  *result = channel;
+  return NS_OK;
+}
+
+////////////////////////////////////////////////////////////////////////////////
diff --git a/image/decoders/icon/nsIconProtocolHandler.h b/image/decoders/icon/nsIconProtocolHandler.h
new file mode 100644
index 0000000000..63843eaa4b
--- /dev/null
+++ b/image/decoders/icon/nsIconProtocolHandler.h
@@ -0,0 +1,25 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_image_decoders_icon_nsIconProtocolHandler_h
+#define mozilla_image_decoders_icon_nsIconProtocolHandler_h
+
+#include "nsWeakReference.h"
+#include "nsIProtocolHandler.h"
+
+class nsIconProtocolHandler : public nsIProtocolHandler,
+                              public nsSupportsWeakReference {
+ public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIPROTOCOLHANDLER
+
+  // nsIconProtocolHandler methods:
+  nsIconProtocolHandler();
+
+ protected:
+  virtual ~nsIconProtocolHandler();
+};
+
+#endif  // mozilla_image_decoders_icon_nsIconProtocolHandler_h
diff --git a/image/decoders/icon/nsIconURI.cpp b/image/decoders/icon/nsIconURI.cpp
new file mode 100644
index 0000000000..d917337bf9
--- /dev/null
+++ b/image/decoders/icon/nsIconURI.cpp
@@ -0,0 +1,654 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set sw=2 sts=2 ts=2 et tw=80:
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsIconURI.h"
+
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/ipc/URIUtils.h"
+#include "mozilla/Sprintf.h"
+
+#include "nsIClassInfoImpl.h"
+#include "nsIIOService.h"
+#include "nsISerializable.h"
+#include "nsIObjectInputStream.h"
+#include "nsIObjectOutputStream.h"
+#include "nsIURL.h"
+#include "nsNetUtil.h"
+#include "plstr.h"
+#include "nsCRT.h"
+#include <stdlib.h>
+
+using namespace mozilla;
+using namespace mozilla::ipc;
+
+#define DEFAULT_IMAGE_SIZE 16
+
+#if defined(MAX_PATH)
+#  define SANE_FILE_NAME_LEN MAX_PATH
+#elif defined(PATH_MAX)
+#  define SANE_FILE_NAME_LEN PATH_MAX
+#else
+#  define SANE_FILE_NAME_LEN 1024
+#endif
+
+static NS_DEFINE_CID(kThisIconURIImplementationCID,
+                     NS_THIS_ICONURI_IMPLEMENTATION_CID);
+
+static const char* const kSizeStrings[] = {"button", "toolbar", "toolbarsmall",
+                                           "menu",   "dnd",     "dialog"};
+
+static const char* const kStateStrings[] = {"normal", "disabled"};
+
+////////////////////////////////////////////////////////////////////////////////
+
+NS_IMPL_CLASSINFO(nsMozIconURI, nullptr, nsIClassInfo::THREADSAFE,
+                  NS_ICONURI_CID)
+// Empty CI getter. We only need nsIClassInfo for Serialization
+NS_IMPL_CI_INTERFACE_GETTER0(nsMozIconURI)
+
+nsMozIconURI::nsMozIconURI()
+    : mSize(DEFAULT_IMAGE_SIZE), mIconSize(-1), mIconState(-1) {}
+
+nsMozIconURI::~nsMozIconURI() {}
+
+NS_IMPL_ADDREF(nsMozIconURI)
+NS_IMPL_RELEASE(nsMozIconURI)
+
+NS_INTERFACE_MAP_BEGIN(nsMozIconURI)
+  if (aIID.Equals(kThisIconURIImplementationCID)) {
+    foundInterface = static_cast<nsIURI*>(this);
+  } else
+    NS_INTERFACE_MAP_ENTRY(nsIMozIconURI)
+  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsIURI)
+  NS_INTERFACE_MAP_ENTRY(nsIURI)
+  NS_INTERFACE_MAP_ENTRY_CONDITIONAL(nsINestedURI, mIconURL)
+  NS_INTERFACE_MAP_ENTRY(nsISerializable)
+  NS_IMPL_QUERY_CLASSINFO(nsMozIconURI)
+NS_INTERFACE_MAP_END
+
+#define MOZICON_SCHEME "moz-icon:"
+#define MOZICON_SCHEME_LEN (sizeof(MOZICON_SCHEME) - 1)
+
+////////////////////////////////////////////////////////////////////////////////
+// nsIURI methods:
+
+NS_IMETHODIMP
+nsMozIconURI::GetSpec(nsACString& aSpec) {
+  aSpec = MOZICON_SCHEME;
+
+  if (mIconURL) {
+    nsAutoCString fileIconSpec;
+    nsresult rv = mIconURL->GetSpec(fileIconSpec);
+    NS_ENSURE_SUCCESS(rv, rv);
+    aSpec += fileIconSpec;
+  } else if (!mStockIcon.IsEmpty()) {
+    aSpec += "//stock/";
+    aSpec += mStockIcon;
+  } else {
+    aSpec += "//";
+    aSpec += mFileName;
+  }
+
+  aSpec += "?size=";
+  if (mIconSize >= 0) {
+    aSpec += kSizeStrings[mIconSize];
+  } else {
+    char buf[20];
+    SprintfLiteral(buf, "%d", mSize);
+    aSpec.Append(buf);
+  }
+
+  if (mIconState >= 0) {
+    aSpec += "&state=";
+    aSpec += kStateStrings[mIconState];
+  }
+
+  if (!mContentType.IsEmpty()) {
+    aSpec += "&contentType=";
+    aSpec += mContentType.get();
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsMozIconURI::GetSpecIgnoringRef(nsACString& result) { return GetSpec(result); }
+
+NS_IMETHODIMP
+nsMozIconURI::GetDisplaySpec(nsACString& aUnicodeSpec) {
+  return GetSpec(aUnicodeSpec);
+}
+
+NS_IMETHODIMP
+nsMozIconURI::GetDisplayHostPort(nsACString& aUnicodeHostPort) {
+  return GetHostPort(aUnicodeHostPort);
+}
+
+NS_IMETHODIMP
+nsMozIconURI::GetDisplayHost(nsACString& aUnicodeHost) {
+  return GetHost(aUnicodeHost);
+}
+
+NS_IMETHODIMP
+nsMozIconURI::GetDisplayPrePath(nsACString& aPrePath) {
+  return GetPrePath(aPrePath);
+}
+
+NS_IMETHODIMP
+nsMozIconURI::GetHasRef(bool* result) {
+  *result = false;
+  return NS_OK;
+}
+
+NS_IMPL_NSIURIMUTATOR_ISUPPORTS(nsMozIconURI::Mutator, nsIURISetters,
+                                nsIURIMutator, nsISerializable)
+
+NS_IMETHODIMP
+nsMozIconURI::Mutate(nsIURIMutator** aMutator) {
+  RefPtr<nsMozIconURI::Mutator> mutator = new nsMozIconURI::Mutator();
+  nsresult rv = mutator->InitFromURI(this);
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+  mutator.forget(aMutator);
+  return NS_OK;
+}
+
+// helper function for parsing out attributes like size, and contentType
+// from the icon url.
+// takes a string like ?size=32&contentType=text/html and returns a new string
+// containing just the attribute value. i.e you could pass in this string with
+// an attribute name of 'size=', this will return 32
+// Assumption: attribute pairs in the string are separated by '&'.
+static void extractAttributeValue(const char* aSearchString,
+                                  const char* aAttributeName,
+                                  nsCString& aResult) {
+  aResult.Truncate();
+
+  if (aSearchString && aAttributeName) {
+    // search the string for attributeName
+    uint32_t attributeNameSize = strlen(aAttributeName);
+    const char* startOfAttribute = PL_strcasestr(aSearchString, aAttributeName);
+    if (startOfAttribute &&
+        (*(startOfAttribute - 1) == '?' || *(startOfAttribute - 1) == '&')) {
+      startOfAttribute += attributeNameSize;  // skip over the attributeName
+      // is there something after the attribute name
+      if (*startOfAttribute) {
+        const char* endofAttribute = strchr(startOfAttribute, '&');
+        if (endofAttribute) {
+          aResult.Assign(Substring(startOfAttribute, endofAttribute));
+        } else {
+          aResult.Assign(startOfAttribute);
+        }
+      }  // if we have a attribute value
+    }    // if we have a attribute name
+  }      // if we got non-null search string and attribute name values
+}
+
+nsresult nsMozIconURI::SetSpecInternal(const nsACString& aSpec) {
+  // Reset everything to default values.
+  mIconURL = nullptr;
+  mSize = DEFAULT_IMAGE_SIZE;
+  mContentType.Truncate();
+  mFileName.Truncate();
+  mStockIcon.Truncate();
+  mIconSize = -1;
+  mIconState = -1;
+
+  nsAutoCString iconSpec(aSpec);
+  if (!Substring(iconSpec, 0, MOZICON_SCHEME_LEN)
+           .EqualsLiteral(MOZICON_SCHEME) ||
+      (!Substring(iconSpec, MOZICON_SCHEME_LEN, 7).EqualsLiteral("file://") &&
+       // Checking for the leading '//' will match both the '//stock/' and
+       // '//.foo' cases:
+       !Substring(iconSpec, MOZICON_SCHEME_LEN, 2).EqualsLiteral("//"))) {
+    return NS_ERROR_MALFORMED_URI;
+  }
+
+  int32_t questionMarkPos = iconSpec.Find("?");
+  if (questionMarkPos != -1 &&
+      static_cast<int32_t>(iconSpec.Length()) > (questionMarkPos + 1)) {
+    extractAttributeValue(iconSpec.get(), "contentType=", mContentType);
+
+    nsAutoCString sizeString;
+    extractAttributeValue(iconSpec.get(), "size=", sizeString);
+    if (!sizeString.IsEmpty()) {
+      const char* sizeStr = sizeString.get();
+      for (uint32_t i = 0; i < ArrayLength(kSizeStrings); i++) {
+        if (nsCRT::strcasecmp(sizeStr, kSizeStrings[i]) == 0) {
+          mIconSize = i;
+          break;
+        }
+      }
+
+      int32_t sizeValue = atoi(sizeString.get());
+      if (sizeValue > 0) {
+        mSize = sizeValue;
+      }
+    }
+
+    nsAutoCString stateString;
+    extractAttributeValue(iconSpec.get(), "state=", stateString);
+    if (!stateString.IsEmpty()) {
+      const char* stateStr = stateString.get();
+      for (uint32_t i = 0; i < ArrayLength(kStateStrings); i++) {
+        if (nsCRT::strcasecmp(stateStr, kStateStrings[i]) == 0) {
+          mIconState = i;
+          break;
+        }
+      }
+    }
+  }
+
+  int32_t pathLength = iconSpec.Length() - MOZICON_SCHEME_LEN;
+  if (questionMarkPos != -1) {
+    pathLength = questionMarkPos - MOZICON_SCHEME_LEN;
+  }
+  if (pathLength < 3) {
+    return NS_ERROR_MALFORMED_URI;
+  }
+
+  nsAutoCString iconPath(Substring(iconSpec, MOZICON_SCHEME_LEN, pathLength));
+
+  // Icon URI path can have three forms:
+  // (1) //stock/<icon-identifier>
+  // (2) //<some dummy file with an extension>
+  // (3) a valid URL
+
+  if (!strncmp("//stock/", iconPath.get(), 8)) {
+    mStockIcon.Assign(Substring(iconPath, 8));
+    // An icon identifier must always be specified.
+    if (mStockIcon.IsEmpty()) {
+      return NS_ERROR_MALFORMED_URI;
+    }
+    return NS_OK;
+  }
+
+  if (StringBeginsWith(iconPath, "//"_ns)) {
+    // Sanity check this supposed dummy file name.
+    if (iconPath.Length() > SANE_FILE_NAME_LEN) {
+      return NS_ERROR_MALFORMED_URI;
+    }
+    iconPath.Cut(0, 2);
+    mFileName.Assign(iconPath);
+  }
+
+  nsresult rv;
+  nsCOMPtr<nsIIOService> ioService(do_GetService(NS_IOSERVICE_CONTRACTID, &rv));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsCOMPtr<nsIURI> uri;
+  ioService->NewURI(iconPath, nullptr, nullptr, getter_AddRefs(uri));
+  mIconURL = do_QueryInterface(uri);
+  if (mIconURL) {
+    // The inner URI should be a 'file:' one. If not, bail.
+    if (!mIconURL->SchemeIs("file")) {
+      return NS_ERROR_MALFORMED_URI;
+    }
+    mFileName.Truncate();
+  } else if (mFileName.IsEmpty()) {
+    return NS_ERROR_MALFORMED_URI;
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsMozIconURI::GetPrePath(nsACString& prePath) {
+  prePath = MOZICON_SCHEME;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsMozIconURI::GetScheme(nsACString& aScheme) {
+  aScheme = "moz-icon";
+  return NS_OK;
+}
+
+nsresult nsMozIconURI::SetScheme(const nsACString& aScheme) {
+  // doesn't make sense to set the scheme of a moz-icon URL
+  return NS_ERROR_FAILURE;
+}
+
+NS_IMETHODIMP
+nsMozIconURI::GetUsername(nsACString& aUsername) { return NS_ERROR_FAILURE; }
+
+nsresult nsMozIconURI::SetUsername(const nsACString& aUsername) {
+  return NS_ERROR_FAILURE;
+}
+
+NS_IMETHODIMP
+nsMozIconURI::GetPassword(nsACString& aPassword) { return NS_ERROR_FAILURE; }
+
+nsresult nsMozIconURI::SetPassword(const nsACString& aPassword) {
+  return NS_ERROR_FAILURE;
+}
+
+NS_IMETHODIMP
+nsMozIconURI::GetUserPass(nsACString& aUserPass) { return NS_ERROR_FAILURE; }
+
+nsresult nsMozIconURI::SetUserPass(const nsACString& aUserPass) {
+  return NS_ERROR_FAILURE;
+}
+
+NS_IMETHODIMP
+nsMozIconURI::GetHostPort(nsACString& aHostPort) { return NS_ERROR_FAILURE; }
+
+nsresult nsMozIconURI::SetHostPort(const nsACString& aHostPort) {
+  return NS_ERROR_FAILURE;
+}
+
+NS_IMETHODIMP
+nsMozIconURI::GetHost(nsACString& aHost) { return NS_ERROR_FAILURE; }
+
+nsresult nsMozIconURI::SetHost(const nsACString& aHost) {
+  return NS_ERROR_FAILURE;
+}
+
+NS_IMETHODIMP
+nsMozIconURI::GetPort(int32_t* aPort) { return NS_ERROR_FAILURE; }
+
+nsresult nsMozIconURI::SetPort(int32_t aPort) { return NS_ERROR_FAILURE; }
+
+NS_IMETHODIMP
+nsMozIconURI::GetPathQueryRef(nsACString& aPath) {
+  aPath.Truncate();
+  return NS_OK;
+}
+
+nsresult nsMozIconURI::SetPathQueryRef(const nsACString& aPath) {
+  return NS_ERROR_FAILURE;
+}
+
+NS_IMETHODIMP
+nsMozIconURI::GetFilePath(nsACString& aFilePath) {
+  aFilePath.Truncate();
+  return NS_OK;
+}
+
+nsresult nsMozIconURI::SetFilePath(const nsACString& aFilePath) {
+  return NS_ERROR_FAILURE;
+}
+
+NS_IMETHODIMP
+nsMozIconURI::GetQuery(nsACString& aQuery) {
+  aQuery.Truncate();
+  return NS_OK;
+}
+
+nsresult nsMozIconURI::SetQuery(const nsACString& aQuery) {
+  return NS_ERROR_FAILURE;
+}
+
+nsresult nsMozIconURI::SetQueryWithEncoding(const nsACString& aQuery,
+                                            const Encoding* aEncoding) {
+  return NS_ERROR_FAILURE;
+}
+
+NS_IMETHODIMP
+nsMozIconURI::GetRef(nsACString& aRef) {
+  aRef.Truncate();
+  return NS_OK;
+}
+
+nsresult nsMozIconURI::SetRef(const nsACString& aRef) {
+  return NS_ERROR_FAILURE;
+}
+
+NS_IMETHODIMP
+nsMozIconURI::Equals(nsIURI* other, bool* result) {
+  *result = false;
+  NS_ENSURE_ARG_POINTER(other);
+  MOZ_ASSERT(result, "null pointer");
+
+  nsAutoCString spec1;
+  nsAutoCString spec2;
+
+  nsresult rv = GetSpec(spec1);
+  NS_ENSURE_SUCCESS(rv, rv);
+  rv = other->GetSpec(spec2);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  if (!nsCRT::strcasecmp(spec1.get(), spec2.get())) {
+    *result = true;
+  } else {
+    *result = false;
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsMozIconURI::EqualsExceptRef(nsIURI* other, bool* result) {
+  // GetRef/SetRef not supported by nsMozIconURI, so
+  // EqualsExceptRef() is the same as Equals().
+  return Equals(other, result);
+}
+
+NS_IMETHODIMP
+nsMozIconURI::SchemeIs(const char* aScheme, bool* aEquals) {
+  MOZ_ASSERT(aEquals, "null pointer");
+  if (!aScheme) {
+    *aEquals = false;
+    return NS_OK;
+  }
+
+  *aEquals = nsCRT::strcasecmp("moz-icon", aScheme) == 0;
+  return NS_OK;
+}
+
+nsresult nsMozIconURI::Clone(nsIURI** result) {
+  nsCOMPtr<nsIURL> newIconURL;
+  if (mIconURL) {
+    newIconURL = mIconURL;
+  }
+
+  RefPtr<nsMozIconURI> uri = new nsMozIconURI();
+  newIconURL.swap(uri->mIconURL);
+  uri->mSize = mSize;
+  uri->mContentType = mContentType;
+  uri->mFileName = mFileName;
+  uri->mStockIcon = mStockIcon;
+  uri->mIconSize = mIconSize;
+  uri->mIconState = mIconState;
+  uri.forget(result);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsMozIconURI::Resolve(const nsACString& relativePath, nsACString& result) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+nsMozIconURI::GetAsciiSpec(nsACString& aSpecA) { return GetSpec(aSpecA); }
+
+NS_IMETHODIMP
+nsMozIconURI::GetAsciiHostPort(nsACString& aHostPortA) {
+  return GetHostPort(aHostPortA);
+}
+
+NS_IMETHODIMP
+nsMozIconURI::GetAsciiHost(nsACString& aHostA) { return GetHost(aHostA); }
+
+////////////////////////////////////////////////////////////////////////////////
+// nsIIconUri methods:
+
+NS_IMETHODIMP
+nsMozIconURI::GetIconURL(nsIURL** aFileUrl) {
+  *aFileUrl = mIconURL;
+  NS_IF_ADDREF(*aFileUrl);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsMozIconURI::GetImageSize(uint32_t* aImageSize)
+// measured by # of pixels in a row. defaults to 16.
+{
+  *aImageSize = mSize;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsMozIconURI::GetContentType(nsACString& aContentType) {
+  aContentType = mContentType;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsMozIconURI::GetFileExtension(nsACString& aFileExtension) {
+  // First, try to get the extension from mIconURL if we have one
+  if (mIconURL) {
+    nsAutoCString fileExt;
+    if (NS_SUCCEEDED(mIconURL->GetFileExtension(fileExt))) {
+      if (!fileExt.IsEmpty()) {
+        // unfortunately, this code doesn't give us the required '.' in
+        // front of the extension so we have to do it ourselves.
+        aFileExtension.Assign('.');
+        aFileExtension.Append(fileExt);
+      }
+    }
+    return NS_OK;
+  }
+
+  if (!mFileName.IsEmpty()) {
+    // truncate the extension out of the file path...
+    const char* chFileName = mFileName.get();  // get the underlying buffer
+    const char* fileExt = strrchr(chFileName, '.');
+    if (!fileExt) {
+      return NS_OK;
+    }
+    aFileExtension = fileExt;
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsMozIconURI::GetStockIcon(nsACString& aStockIcon) {
+  aStockIcon = mStockIcon;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsMozIconURI::GetIconSize(nsACString& aSize) {
+  if (mIconSize >= 0) {
+    aSize = kSizeStrings[mIconSize];
+  } else {
+    aSize.Truncate();
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsMozIconURI::GetIconState(nsACString& aState) {
+  if (mIconState >= 0) {
+    aState = kStateStrings[mIconState];
+  } else {
+    aState.Truncate();
+  }
+  return NS_OK;
+}
+
+void nsMozIconURI::Serialize(URIParams& aParams) {
+  IconURIParams params;
+
+  if (mIconURL) {
+    URIParams iconURLParams;
+    SerializeURI(mIconURL, iconURLParams);
+    if (iconURLParams.type() == URIParams::T__None) {
+      // Serialization failed, bail.
+      return;
+    }
+
+    params.uri() = Some(std::move(iconURLParams));
+  } else {
+    params.uri() = Nothing();
+  }
+
+  params.size() = mSize;
+  params.fileName() = mFileName;
+  params.stockIcon() = mStockIcon;
+  params.iconSize() = mIconSize;
+  params.iconState() = mIconState;
+
+  aParams = params;
+}
+
+bool nsMozIconURI::Deserialize(const URIParams& aParams) {
+  if (aParams.type() != URIParams::TIconURIParams) {
+    MOZ_ASSERT_UNREACHABLE("Received unknown URI from other process!");
+    return false;
+  }
+
+  const IconURIParams& params = aParams.get_IconURIParams();
+  if (params.uri().isSome()) {
+    nsCOMPtr<nsIURI> uri = DeserializeURI(params.uri().ref());
+    mIconURL = do_QueryInterface(uri);
+    if (!mIconURL) {
+      MOZ_ASSERT_UNREACHABLE("bad nsIURI passed");
+      return false;
+    }
+  }
+
+  mSize = params.size();
+  mContentType = params.contentType();
+  mFileName = params.fileName();
+  mStockIcon = params.stockIcon();
+
+  if (params.iconSize() < -1 ||
+      params.iconSize() >= (int32_t)ArrayLength(kSizeStrings)) {
+    return false;
+  }
+  mIconSize = params.iconSize();
+
+  if (params.iconState() < -1 ||
+      params.iconState() >= (int32_t)ArrayLength(kStateStrings)) {
+    return false;
+  }
+  mIconState = params.iconState();
+
+  return true;
+}
+
+NS_IMETHODIMP
+nsMozIconURI::GetInnerURI(nsIURI** aURI) {
+  nsCOMPtr<nsIURI> iconURL = mIconURL;
+  if (!iconURL) {
+    *aURI = nullptr;
+    return NS_ERROR_FAILURE;
+  }
+
+  iconURL.forget(aURI);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsMozIconURI::GetInnermostURI(nsIURI** aURI) {
+  return NS_ImplGetInnermostURI(this, aURI);
+}
+
+NS_IMETHODIMP
+nsMozIconURI::Read(nsIObjectInputStream* aStream) {
+  MOZ_ASSERT_UNREACHABLE("Use nsIURIMutator.read() instead");
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+nsresult nsMozIconURI::ReadPrivate(nsIObjectInputStream* aStream) {
+  nsAutoCString spec;
+  nsresult rv = aStream->ReadCString(spec);
+  NS_ENSURE_SUCCESS(rv, rv);
+  return SetSpecInternal(spec);
+}
+
+NS_IMETHODIMP
+nsMozIconURI::Write(nsIObjectOutputStream* aStream) {
+  nsAutoCString spec;
+  nsresult rv = GetSpec(spec);
+  NS_ENSURE_SUCCESS(rv, rv);
+  return aStream->WriteStringZ(spec.get());
+}
diff --git a/image/decoders/icon/nsIconURI.h b/image/decoders/icon/nsIconURI.h
new file mode 100644
index 0000000000..1f55bc686c
--- /dev/null
+++ b/image/decoders/icon/nsIconURI.h
@@ -0,0 +1,118 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_image_decoders_icon_nsIconURI_h
+#define mozilla_image_decoders_icon_nsIconURI_h
+
+#include "nsIIconURI.h"
+#include "nsCOMPtr.h"
+#include "nsString.h"
+#include "nsINestedURI.h"
+#include "nsIURIMutator.h"
+#include "nsISerializable.h"
+
+#define NS_THIS_ICONURI_IMPLEMENTATION_CID           \
+  { /* 0b9bb0c2-fee6-470b-b9b9-9fd9462b5e19 */       \
+    0x5c3e417f, 0xb686, 0x4105, {                    \
+      0x86, 0xe7, 0xf9, 0x1b, 0xac, 0x97, 0x4d, 0x5c \
+    }                                                \
+  }
+
+namespace mozilla {
+class Encoding;
+}
+
+class nsMozIconURI final : public nsIMozIconURI,
+                           public nsINestedURI,
+                           public nsISerializable {
+ public:
+  NS_DECL_THREADSAFE_ISUPPORTS
+  NS_DECL_NSIURI
+  NS_DECL_NSIMOZICONURI
+  NS_DECL_NSINESTEDURI
+  NS_DECL_NSISERIALIZABLE
+
+ protected:
+  nsMozIconURI();
+  virtual ~nsMozIconURI();
+  nsCOMPtr<nsIURL> mIconURL;  // a URL that we want the icon for
+  uint32_t mSize;  // the # of pixels in a row that we want for this image.
+                   // Typically 16, 32, 128, etc.
+  nsCString mContentType;  // optional field explicitly specifying the content
+                           // type
+  nsCString mFileName;  // for if we don't have an actual file path, we're just
+                        // given a filename with an extension
+  nsCString mStockIcon;
+  int32_t mIconSize;   // -1 if not specified, otherwise index into
+                       // kSizeStrings
+  int32_t mIconState;  // -1 if not specified, otherwise index into
+                       // kStateStrings
+
+ private:
+  nsresult Clone(nsIURI** aURI);
+  nsresult SetSpecInternal(const nsACString& input);
+  nsresult SetScheme(const nsACString& input);
+  nsresult SetUserPass(const nsACString& input);
+  nsresult SetUsername(const nsACString& input);
+  nsresult SetPassword(const nsACString& input);
+  nsresult SetHostPort(const nsACString& aValue);
+  nsresult SetHost(const nsACString& input);
+  nsresult SetPort(int32_t port);
+  nsresult SetPathQueryRef(const nsACString& input);
+  nsresult SetRef(const nsACString& input);
+  nsresult SetFilePath(const nsACString& input);
+  nsresult SetQuery(const nsACString& input);
+  nsresult SetQueryWithEncoding(const nsACString& input,
+                                const mozilla::Encoding* encoding);
+  nsresult ReadPrivate(nsIObjectInputStream* stream);
+  bool Deserialize(const mozilla::ipc::URIParams&);
+
+ public:
+  class Mutator final : public nsIURIMutator,
+                        public BaseURIMutator<nsMozIconURI>,
+                        public nsISerializable {
+    NS_DECL_ISUPPORTS
+    NS_FORWARD_SAFE_NSIURISETTERS_RET(mURI)
+
+    NS_IMETHOD
+    Write(nsIObjectOutputStream* aOutputStream) override {
+      return NS_ERROR_NOT_IMPLEMENTED;
+    }
+
+    [[nodiscard]] NS_IMETHOD Read(nsIObjectInputStream* aStream) override {
+      return InitFromInputStream(aStream);
+    }
+
+    NS_IMETHOD Deserialize(const mozilla::ipc::URIParams& aParams) override {
+      return InitFromIPCParams(aParams);
+    }
+
+    NS_IMETHOD Finalize(nsIURI** aURI) override {
+      mURI.forget(aURI);
+      return NS_OK;
+    }
+
+    NS_IMETHOD SetSpec(const nsACString& aSpec,
+                       nsIURIMutator** aMutator) override {
+      if (aMutator) {
+        nsCOMPtr<nsIURIMutator> mutator = this;
+        mutator.forget(aMutator);
+      }
+      return InitFromSpec(aSpec);
+    }
+
+    explicit Mutator() {}
+
+   private:
+    virtual ~Mutator() {}
+
+    friend class nsMozIconURI;
+  };
+
+  friend BaseURIMutator<nsMozIconURI>;
+};
+
+#endif  // mozilla_image_decoders_icon_nsIconURI_h
diff --git a/image/decoders/icon/win/moz.build b/image/decoders/icon/win/moz.build
new file mode 100644
index 0000000000..c4472f89ac
--- /dev/null
+++ b/image/decoders/icon/win/moz.build
@@ -0,0 +1,21 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+SOURCES += [
+    "nsIconChannel.cpp",
+]
+
+EXPORTS += [
+    "nsIconChannel.h",
+]
+
+LOCAL_INCLUDES += [
+    "/image",
+]
+
+FINAL_LIBRARY = "xul"
+
+include("/ipc/chromium/chromium-config.mozbuild")
diff --git a/image/decoders/icon/win/nsIconChannel.cpp b/image/decoders/icon/win/nsIconChannel.cpp
new file mode 100644
index 0000000000..fe76afe9b1
--- /dev/null
+++ b/image/decoders/icon/win/nsIconChannel.cpp
@@ -0,0 +1,1006 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/BasePrincipal.h"
+#include "mozilla/Monitor.h"
+#include "mozilla/SyncRunnable.h"
+#include "mozilla/UniquePtr.h"
+#include "mozilla/UniquePtrExtensions.h"
+#include "mozilla/WindowsProcessMitigations.h"
+#include "mozilla/dom/ContentChild.h"
+#include "mozilla/ipc/ByteBuf.h"
+
+#include "nsComponentManagerUtils.h"
+#include "nsIconChannel.h"
+#include "nsIIconURI.h"
+#include "nsIInterfaceRequestor.h"
+#include "nsIInterfaceRequestorUtils.h"
+#include "nsString.h"
+#include "nsReadableUtils.h"
+#include "nsMimeTypes.h"
+#include "nsIURL.h"
+#include "nsIPipe.h"
+#include "nsNetCID.h"
+#include "nsIFile.h"
+#include "nsIFileURL.h"
+#include "nsIIconURI.h"
+#include "nsIAsyncInputStream.h"
+#include "nsIAsyncOutputStream.h"
+#include "nsIMIMEService.h"
+#include "nsCExternalHandlerService.h"
+#include "nsDirectoryServiceDefs.h"
+#include "nsProxyRelease.h"
+#include "nsContentSecurityManager.h"
+#include "nsContentUtils.h"
+#include "nsNetUtil.h"
+#include "nsThreadUtils.h"
+
+#include "Decoder.h"
+#include "DecodePool.h"
+
+// we need windows.h to read out registry information...
+#include <windows.h>
+#include <shellapi.h>
+#include <shlobj.h>
+#include <objbase.h>
+#include <wchar.h>
+
+using namespace mozilla;
+using namespace mozilla::image;
+
+using mozilla::ipc::ByteBuf;
+
+struct ICONFILEHEADER {
+  uint16_t ifhReserved;
+  uint16_t ifhType;
+  uint16_t ifhCount;
+};
+
+struct ICONENTRY {
+  int8_t ieWidth;
+  int8_t ieHeight;
+  uint8_t ieColors;
+  uint8_t ieReserved;
+  uint16_t iePlanes;
+  uint16_t ieBitCount;
+  uint32_t ieSizeImage;
+  uint32_t ieFileOffset;
+};
+
+struct IconPathInfo {
+  nsCOMPtr<nsIFile> localFile;
+  nsAutoString filePath;
+  UINT infoFlags = 0;
+};
+
+using HIconPromise = MozPromise<HICON, nsresult, true>;
+
+static UINT GetSizeInfoFlag(uint32_t aDesiredImageSize) {
+  return aDesiredImageSize > 16 ? SHGFI_SHELLICONSIZE : SHGFI_SMALLICON;
+}
+
+static nsresult ExtractIconInfoFromUrl(nsIURI* aUrl, nsIFile** aLocalFile,
+                                       uint32_t* aDesiredImageSize,
+                                       nsCString& aContentType,
+                                       nsCString& aFileExtension) {
+  nsresult rv = NS_OK;
+  nsCOMPtr<nsIMozIconURI> iconURI(do_QueryInterface(aUrl, &rv));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  iconURI->GetImageSize(aDesiredImageSize);
+  iconURI->GetContentType(aContentType);
+  iconURI->GetFileExtension(aFileExtension);
+
+  nsCOMPtr<nsIURL> url;
+  rv = iconURI->GetIconURL(getter_AddRefs(url));
+  if (NS_FAILED(rv) || !url) return NS_OK;
+
+  nsCOMPtr<nsIFileURL> fileURL = do_QueryInterface(url, &rv);
+  if (NS_FAILED(rv) || !fileURL) return NS_OK;
+
+  nsCOMPtr<nsIFile> file;
+  rv = fileURL->GetFile(getter_AddRefs(file));
+  if (NS_FAILED(rv) || !file) return NS_OK;
+
+  return file->Clone(aLocalFile);
+}
+
+static nsresult ExtractIconPathInfoFromUrl(nsIURI* aUrl,
+                                           IconPathInfo* aIconPathInfo) {
+  nsCString contentType;
+  nsCString fileExt;
+  nsCOMPtr<nsIFile> localFile;  // file we want an icon for
+  uint32_t desiredImageSize;
+  nsresult rv = ExtractIconInfoFromUrl(aUrl, getter_AddRefs(localFile),
+                                       &desiredImageSize, contentType, fileExt);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // if the file exists, we are going to use it's real attributes...
+  // otherwise we only want to use it for it's extension...
+  UINT infoFlags = SHGFI_ICON;
+
+  bool fileExists = false;
+
+  nsAutoString filePath;
+  CopyASCIItoUTF16(fileExt, filePath);
+  if (localFile) {
+    rv = localFile->Normalize();
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    localFile->GetPath(filePath);
+    if (filePath.Length() < 2 || filePath[1] != ':') {
+      return NS_ERROR_MALFORMED_URI;  // UNC
+    }
+
+    if (filePath.Last() == ':') {
+      filePath.Append('\\');
+    } else {
+      localFile->Exists(&fileExists);
+      if (!fileExists) {
+        localFile->GetLeafName(filePath);
+      }
+    }
+  }
+
+  if (!fileExists) {
+    infoFlags |= SHGFI_USEFILEATTRIBUTES;
+  }
+
+  infoFlags |= GetSizeInfoFlag(desiredImageSize);
+
+  // if we have a content type... then use it! but for existing files,
+  // we want to show their real icon.
+  if (!fileExists && !contentType.IsEmpty()) {
+    nsCOMPtr<nsIMIMEService> mimeService(
+        do_GetService(NS_MIMESERVICE_CONTRACTID, &rv));
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    nsAutoCString defFileExt;
+    mimeService->GetPrimaryExtension(contentType, fileExt, defFileExt);
+    // If the mime service does not know about this mime type, we show
+    // the generic icon.
+    // In any case, we need to insert a '.' before the extension.
+    filePath = u"."_ns + NS_ConvertUTF8toUTF16(defFileExt);
+  }
+
+  if (!localFile && !fileExists &&
+      ((filePath.Length() == 1 && filePath.Last() == '.') ||
+       filePath.Length() == 0)) {
+    filePath = u".MozBogusExtensionMoz"_ns;
+  }
+
+  aIconPathInfo->localFile = std::move(localFile);
+  aIconPathInfo->filePath = std::move(filePath);
+  aIconPathInfo->infoFlags = infoFlags;
+
+  return NS_OK;
+}
+
+static bool GetSpecialFolderIcon(nsIFile* aFile, int aFolder, UINT aInfoFlags,
+                                 HICON* aIcon) {
+  if (!aFile) {
+    return false;
+  }
+
+  wchar_t fileNativePath[MAX_PATH];
+  nsAutoString fileNativePathStr;
+  aFile->GetPath(fileNativePathStr);
+  ::GetShortPathNameW(fileNativePathStr.get(), fileNativePath,
+                      ArrayLength(fileNativePath));
+
+  struct IdListDeleter {
+    void operator()(ITEMIDLIST* ptr) { ::CoTaskMemFree(ptr); }
+  };
+
+  UniquePtr<ITEMIDLIST, IdListDeleter> idList;
+  HRESULT hr =
+      ::SHGetSpecialFolderLocation(nullptr, aFolder, getter_Transfers(idList));
+  if (FAILED(hr)) {
+    return false;
+  }
+
+  wchar_t specialNativePath[MAX_PATH];
+  ::SHGetPathFromIDListW(idList.get(), specialNativePath);
+  ::GetShortPathNameW(specialNativePath, specialNativePath,
+                      ArrayLength(specialNativePath));
+
+  if (wcsicmp(fileNativePath, specialNativePath) != 0) {
+    return false;
+  }
+
+  SHFILEINFOW sfi = {};
+  aInfoFlags |= (SHGFI_PIDL | SHGFI_SYSICONINDEX);
+  if (::SHGetFileInfoW((LPCWSTR)(LPCITEMIDLIST)idList.get(), 0, &sfi,
+                       sizeof(sfi), aInfoFlags) == 0) {
+    return false;
+  }
+
+  *aIcon = sfi.hIcon;
+  return true;
+}
+
+static nsresult GetIconHandleFromPathInfo(const IconPathInfo& aPathInfo,
+                                          HICON* aIcon) {
+  MOZ_DIAGNOSTIC_ASSERT(!IsWin32kLockedDown());
+
+  // Is this the "Desktop" folder?
+  if (GetSpecialFolderIcon(aPathInfo.localFile, CSIDL_DESKTOP,
+                           aPathInfo.infoFlags, aIcon)) {
+    return NS_OK;
+  }
+
+  // Is this the "My Documents" folder?
+  if (GetSpecialFolderIcon(aPathInfo.localFile, CSIDL_PERSONAL,
+                           aPathInfo.infoFlags, aIcon)) {
+    return NS_OK;
+  }
+
+  // There are other "Special Folders" and Namespace entities that we
+  // are not fetching icons for, see:
+  // http://msdn.microsoft.com/library/default.asp?url=/library/en-us/
+  //        shellcc/platform/shell/reference/enums/csidl.asp
+  // If we ever need to get them, code to do so would be inserted here.
+
+  // Not a special folder, or something else failed above.
+  SHFILEINFOW sfi = {};
+  if (::SHGetFileInfoW(aPathInfo.filePath.get(), FILE_ATTRIBUTE_ARCHIVE, &sfi,
+                       sizeof(sfi), aPathInfo.infoFlags) != 0) {
+    *aIcon = sfi.hIcon;
+    return NS_OK;
+  }
+
+  return NS_ERROR_NOT_AVAILABLE;
+}
+
+// Match stock icons with names
+static mozilla::Maybe<SHSTOCKICONID> GetStockIconIDForName(
+    const nsACString& aStockName) {
+  return aStockName.EqualsLiteral("uac-shield") ? Some(SIID_SHIELD) : Nothing();
+}
+
+// Specific to Vista and above
+static nsresult GetStockHIcon(nsIMozIconURI* aIconURI, HICON* aIcon) {
+  uint32_t desiredImageSize;
+  aIconURI->GetImageSize(&desiredImageSize);
+  nsAutoCString stockIcon;
+  aIconURI->GetStockIcon(stockIcon);
+
+  Maybe<SHSTOCKICONID> stockIconID = GetStockIconIDForName(stockIcon);
+  if (stockIconID.isNothing()) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  UINT infoFlags = SHGSI_ICON;
+  infoFlags |= GetSizeInfoFlag(desiredImageSize);
+
+  SHSTOCKICONINFO sii = {0};
+  sii.cbSize = sizeof(sii);
+  HRESULT hr = SHGetStockIconInfo(*stockIconID, infoFlags, &sii);
+  if (FAILED(hr)) {
+    return NS_ERROR_FAILURE;
+  }
+
+  *aIcon = sii.hIcon;
+
+  return NS_OK;
+}
+
+// Given a BITMAPINFOHEADER, returns the size of the color table.
+static int GetColorTableSize(BITMAPINFOHEADER* aHeader) {
+  int colorTableSize = -1;
+
+  // http://msdn.microsoft.com/en-us/library/dd183376%28v=VS.85%29.aspx
+  switch (aHeader->biBitCount) {
+    case 0:
+      colorTableSize = 0;
+      break;
+    case 1:
+      colorTableSize = 2 * sizeof(RGBQUAD);
+      break;
+    case 4:
+    case 8: {
+      // The maximum possible size for the color table is 2**bpp, so check for
+      // that and fail if we're not in those bounds
+      unsigned int maxEntries = 1 << (aHeader->biBitCount);
+      if (aHeader->biClrUsed > 0 && aHeader->biClrUsed <= maxEntries) {
+        colorTableSize = aHeader->biClrUsed * sizeof(RGBQUAD);
+      } else if (aHeader->biClrUsed == 0) {
+        colorTableSize = maxEntries * sizeof(RGBQUAD);
+      }
+      break;
+    }
+    case 16:
+    case 32:
+      // If we have BI_BITFIELDS compression, we would normally need 3 DWORDS
+      // for the bitfields mask which would be stored in the color table;
+      // However, we instead force the bitmap to request data of type BI_RGB so
+      // the color table should be of size 0. Setting aHeader->biCompression =
+      // BI_RGB forces the later call to GetDIBits to return to us BI_RGB data.
+      if (aHeader->biCompression == BI_BITFIELDS) {
+        aHeader->biCompression = BI_RGB;
+      }
+      colorTableSize = 0;
+      break;
+    case 24:
+      colorTableSize = 0;
+      break;
+  }
+
+  if (colorTableSize < 0) {
+    NS_WARNING("Unable to figure out the color table size for this bitmap");
+  }
+
+  return colorTableSize;
+}
+
+// Given a header and a size, creates a freshly allocated BITMAPINFO structure.
+// It is the caller's responsibility to null-check and delete the structure.
+static BITMAPINFO* CreateBitmapInfo(BITMAPINFOHEADER* aHeader,
+                                    size_t aColorTableSize) {
+  BITMAPINFO* bmi = (BITMAPINFO*)::operator new(
+      sizeof(BITMAPINFOHEADER) + aColorTableSize, mozilla::fallible);
+  if (bmi) {
+    memcpy(bmi, aHeader, sizeof(BITMAPINFOHEADER));
+    memset(bmi->bmiColors, 0, aColorTableSize);
+  }
+  return bmi;
+}
+
+static nsresult MakeIconBuffer(HICON aIcon, ByteBuf* aOutBuffer) {
+  nsresult rv = NS_ERROR_FAILURE;
+
+  if (aIcon) {
+    // we got a handle to an icon. Now we want to get a bitmap for the icon
+    // using GetIconInfo....
+    ICONINFO iconInfo;
+    if (GetIconInfo(aIcon, &iconInfo)) {
+      // we got the bitmaps, first find out their size
+      HDC hDC = CreateCompatibleDC(nullptr);  // get a device context for
+                                              // the screen.
+      BITMAPINFOHEADER maskHeader = {sizeof(BITMAPINFOHEADER)};
+      BITMAPINFOHEADER colorHeader = {sizeof(BITMAPINFOHEADER)};
+      int colorTableSize, maskTableSize;
+      if (GetDIBits(hDC, iconInfo.hbmMask, 0, 0, nullptr,
+                    (BITMAPINFO*)&maskHeader, DIB_RGB_COLORS) &&
+          GetDIBits(hDC, iconInfo.hbmColor, 0, 0, nullptr,
+                    (BITMAPINFO*)&colorHeader, DIB_RGB_COLORS) &&
+          maskHeader.biHeight == colorHeader.biHeight &&
+          maskHeader.biWidth == colorHeader.biWidth &&
+          colorHeader.biBitCount > 8 && colorHeader.biSizeImage > 0 &&
+          colorHeader.biWidth >= 0 && colorHeader.biWidth <= 255 &&
+          colorHeader.biHeight >= 0 && colorHeader.biHeight <= 255 &&
+          maskHeader.biSizeImage > 0 &&
+          (colorTableSize = GetColorTableSize(&colorHeader)) >= 0 &&
+          (maskTableSize = GetColorTableSize(&maskHeader)) >= 0) {
+        uint32_t iconSize = sizeof(ICONFILEHEADER) + sizeof(ICONENTRY) +
+                            sizeof(BITMAPINFOHEADER) + colorHeader.biSizeImage +
+                            maskHeader.biSizeImage;
+
+        if (!aOutBuffer->Allocate(iconSize)) {
+          rv = NS_ERROR_OUT_OF_MEMORY;
+        } else {
+          uint8_t* whereTo = aOutBuffer->mData;
+          int howMuch;
+
+          // the data starts with an icon file header
+          ICONFILEHEADER iconHeader;
+          iconHeader.ifhReserved = 0;
+          iconHeader.ifhType = 1;
+          iconHeader.ifhCount = 1;
+          howMuch = sizeof(ICONFILEHEADER);
+          memcpy(whereTo, &iconHeader, howMuch);
+          whereTo += howMuch;
+
+          // followed by the single icon entry
+          ICONENTRY iconEntry;
+          iconEntry.ieWidth = static_cast<int8_t>(colorHeader.biWidth);
+          iconEntry.ieHeight = static_cast<int8_t>(colorHeader.biHeight);
+          iconEntry.ieColors = 0;
+          iconEntry.ieReserved = 0;
+          iconEntry.iePlanes = 1;
+          iconEntry.ieBitCount = colorHeader.biBitCount;
+          iconEntry.ieSizeImage = sizeof(BITMAPINFOHEADER) +
+                                  colorHeader.biSizeImage +
+                                  maskHeader.biSizeImage;
+          iconEntry.ieFileOffset = sizeof(ICONFILEHEADER) + sizeof(ICONENTRY);
+          howMuch = sizeof(ICONENTRY);
+          memcpy(whereTo, &iconEntry, howMuch);
+          whereTo += howMuch;
+
+          // followed by the bitmap info header
+          // (doubling the height because icons have two bitmaps)
+          colorHeader.biHeight *= 2;
+          colorHeader.biSizeImage += maskHeader.biSizeImage;
+          howMuch = sizeof(BITMAPINFOHEADER);
+          memcpy(whereTo, &colorHeader, howMuch);
+          whereTo += howMuch;
+          colorHeader.biHeight /= 2;
+          colorHeader.biSizeImage -= maskHeader.biSizeImage;
+
+          // followed by the XOR bitmap data (colorHeader)
+          // (you'd expect the color table to come here, but it apparently
+          // doesn't)
+          BITMAPINFO* colorInfo =
+              CreateBitmapInfo(&colorHeader, colorTableSize);
+          if (colorInfo &&
+              GetDIBits(hDC, iconInfo.hbmColor, 0, colorHeader.biHeight,
+                        whereTo, colorInfo, DIB_RGB_COLORS)) {
+            whereTo += colorHeader.biSizeImage;
+
+            // and finally the AND bitmap data (maskHeader)
+            BITMAPINFO* maskInfo = CreateBitmapInfo(&maskHeader, maskTableSize);
+            if (maskInfo &&
+                GetDIBits(hDC, iconInfo.hbmMask, 0, maskHeader.biHeight,
+                          whereTo, maskInfo, DIB_RGB_COLORS)) {
+              rv = NS_OK;
+            }  // if we got bitmap bits
+            delete maskInfo;
+          }  // if we got mask bits
+          delete colorInfo;
+        }  // if we allocated the buffer
+      }    // if we got mask size
+
+      DeleteDC(hDC);
+      DeleteObject(iconInfo.hbmColor);
+      DeleteObject(iconInfo.hbmMask);
+    }  // if we got icon info
+    DestroyIcon(aIcon);
+  }  // if we got an hIcon
+
+  return rv;
+}
+
+static nsresult GetIconHandleFromURLBlocking(nsIMozIconURI* aUrl,
+                                             HICON* aIcon) {
+  nsAutoCString stockIcon;
+  aUrl->GetStockIcon(stockIcon);
+  if (!stockIcon.IsEmpty()) {
+    return GetStockHIcon(aUrl, aIcon);
+  }
+
+  IconPathInfo iconPathInfo;
+  nsresult rv = ExtractIconPathInfoFromUrl(aUrl, &iconPathInfo);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsCOMPtr<nsIRunnable> task = NS_NewRunnableFunction(
+      "GetIconHandleFromURLBlocking",
+      [&] { rv = GetIconHandleFromPathInfo(iconPathInfo, aIcon); });
+
+  RefPtr<nsIEventTarget> target = DecodePool::Singleton()->GetIOEventTarget();
+
+  nsresult dispatchResult = SyncRunnable::DispatchToThread(target, task);
+  NS_ENSURE_SUCCESS(dispatchResult, dispatchResult);
+
+  return rv;
+}
+
+static RefPtr<HIconPromise> GetIconHandleFromURLAsync(nsIMozIconURI* aUrl) {
+  RefPtr<HIconPromise::Private> promise = new HIconPromise::Private(__func__);
+
+  nsAutoCString stockIcon;
+  aUrl->GetStockIcon(stockIcon);
+  if (!stockIcon.IsEmpty()) {
+    HICON hIcon = nullptr;
+    nsresult rv = GetStockHIcon(aUrl, &hIcon);
+    if (NS_SUCCEEDED(rv)) {
+      promise->Resolve(hIcon, __func__);
+    } else {
+      promise->Reject(rv, __func__);
+    }
+    return promise;
+  }
+
+  IconPathInfo iconPathInfo;
+  nsresult rv = ExtractIconPathInfoFromUrl(aUrl, &iconPathInfo);
+  if (NS_FAILED(rv)) {
+    promise->Reject(rv, __func__);
+    return promise;
+  }
+
+  nsCOMPtr<nsIRunnable> task = NS_NewRunnableFunction(
+      "GetIconHandleFromURLAsync", [iconPathInfo, promise] {
+        HICON hIcon = nullptr;
+        nsresult rv = GetIconHandleFromPathInfo(iconPathInfo, &hIcon);
+        if (NS_SUCCEEDED(rv)) {
+          promise->Resolve(hIcon, __func__);
+        } else {
+          promise->Reject(rv, __func__);
+        }
+      });
+
+  RefPtr<nsIEventTarget> target = DecodePool::Singleton()->GetIOEventTarget();
+
+  rv = target->Dispatch(task.forget(), NS_DISPATCH_NORMAL);
+  if (NS_FAILED(rv)) {
+    promise->Reject(rv, __func__);
+  }
+
+  return promise;
+}
+
+static RefPtr<nsIconChannel::ByteBufPromise> GetIconBufferFromURLAsync(
+    nsIMozIconURI* aUrl) {
+  RefPtr<nsIconChannel::ByteBufPromise::Private> promise =
+      new nsIconChannel::ByteBufPromise::Private(__func__);
+
+  GetIconHandleFromURLAsync(aUrl)->Then(
+      GetCurrentSerialEventTarget(), __func__,
+      [promise](HICON aIcon) {
+        ByteBuf iconBuffer;
+        nsresult rv = MakeIconBuffer(aIcon, &iconBuffer);
+        if (NS_SUCCEEDED(rv)) {
+          promise->Resolve(std::move(iconBuffer), __func__);
+        } else {
+          promise->Reject(rv, __func__);
+        }
+      },
+      [promise](nsresult rv) { promise->Reject(rv, __func__); });
+
+  return promise;
+}
+
+static nsresult WriteByteBufToOutputStream(const ByteBuf& aBuffer,
+                                           nsIAsyncOutputStream* aStream) {
+  uint32_t written = 0;
+  nsresult rv = aStream->Write(reinterpret_cast<const char*>(aBuffer.mData),
+                               aBuffer.mLen, &written);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  return (written == aBuffer.mLen) ? NS_OK : NS_ERROR_UNEXPECTED;
+}
+
+NS_IMPL_ISUPPORTS(nsIconChannel, nsIChannel, nsIRequest, nsIRequestObserver,
+                  nsIStreamListener)
+
+// nsIconChannel methods
+nsIconChannel::nsIconChannel() {}
+
+nsIconChannel::~nsIconChannel() {
+  if (mLoadInfo) {
+    NS_ReleaseOnMainThread("nsIconChannel::mLoadInfo", mLoadInfo.forget());
+  }
+  if (mLoadGroup) {
+    NS_ReleaseOnMainThread("nsIconChannel::mLoadGroup", mLoadGroup.forget());
+  }
+}
+
+nsresult nsIconChannel::Init(nsIURI* uri) {
+  NS_ASSERTION(uri, "no uri");
+  mUrl = uri;
+  mOriginalURI = uri;
+  nsresult rv;
+  mPump = do_CreateInstance(NS_INPUTSTREAMPUMP_CONTRACTID, &rv);
+  return rv;
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// nsIRequest methods:
+
+NS_IMETHODIMP
+nsIconChannel::GetName(nsACString& result) { return mUrl->GetSpec(result); }
+
+NS_IMETHODIMP
+nsIconChannel::IsPending(bool* result) { return mPump->IsPending(result); }
+
+NS_IMETHODIMP
+nsIconChannel::GetStatus(nsresult* status) { return mPump->GetStatus(status); }
+
+NS_IMETHODIMP nsIconChannel::SetCanceledReason(const nsACString& aReason) {
+  return SetCanceledReasonImpl(aReason);
+}
+
+NS_IMETHODIMP nsIconChannel::GetCanceledReason(nsACString& aReason) {
+  return GetCanceledReasonImpl(aReason);
+}
+
+NS_IMETHODIMP nsIconChannel::CancelWithReason(nsresult aStatus,
+                                              const nsACString& aReason) {
+  return CancelWithReasonImpl(aStatus, aReason);
+}
+
+NS_IMETHODIMP
+nsIconChannel::Cancel(nsresult status) {
+  mCanceled = true;
+  return mPump->Cancel(status);
+}
+
+NS_IMETHODIMP
+nsIconChannel::GetCanceled(bool* result) {
+  *result = mCanceled;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsIconChannel::Suspend(void) { return mPump->Suspend(); }
+
+NS_IMETHODIMP
+nsIconChannel::Resume(void) { return mPump->Resume(); }
+NS_IMETHODIMP
+nsIconChannel::GetLoadGroup(nsILoadGroup** aLoadGroup) {
+  *aLoadGroup = mLoadGroup;
+  NS_IF_ADDREF(*aLoadGroup);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsIconChannel::SetLoadGroup(nsILoadGroup* aLoadGroup) {
+  mLoadGroup = aLoadGroup;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsIconChannel::GetLoadFlags(uint32_t* aLoadAttributes) {
+  return mPump->GetLoadFlags(aLoadAttributes);
+}
+
+NS_IMETHODIMP
+nsIconChannel::SetLoadFlags(uint32_t aLoadAttributes) {
+  return mPump->SetLoadFlags(aLoadAttributes);
+}
+
+NS_IMETHODIMP
+nsIconChannel::GetTRRMode(nsIRequest::TRRMode* aTRRMode) {
+  return GetTRRModeImpl(aTRRMode);
+}
+
+NS_IMETHODIMP
+nsIconChannel::SetTRRMode(nsIRequest::TRRMode aTRRMode) {
+  return SetTRRModeImpl(aTRRMode);
+}
+
+NS_IMETHODIMP
+nsIconChannel::GetIsDocument(bool* aIsDocument) {
+  return NS_GetIsDocumentChannel(this, aIsDocument);
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// nsIChannel methods:
+
+NS_IMETHODIMP
+nsIconChannel::GetOriginalURI(nsIURI** aURI) {
+  *aURI = mOriginalURI;
+  NS_ADDREF(*aURI);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsIconChannel::SetOriginalURI(nsIURI* aURI) {
+  NS_ENSURE_ARG_POINTER(aURI);
+  mOriginalURI = aURI;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsIconChannel::GetURI(nsIURI** aURI) {
+  *aURI = mUrl;
+  NS_IF_ADDREF(*aURI);
+  return NS_OK;
+}
+
+// static
+RefPtr<nsIconChannel::ByteBufPromise> nsIconChannel::GetIconAsync(
+    nsIURI* aURI) {
+  MOZ_ASSERT(XRE_IsParentProcess());
+
+  nsresult rv = NS_OK;
+  nsCOMPtr<nsIMozIconURI> iconURI(do_QueryInterface(aURI, &rv));
+  if (NS_FAILED(rv)) {
+    return ByteBufPromise::CreateAndReject(rv, __func__);
+  }
+
+  return GetIconBufferFromURLAsync(iconURI);
+}
+
+NS_IMETHODIMP
+nsIconChannel::Open(nsIInputStream** aStream) {
+  nsCOMPtr<nsIStreamListener> listener;
+  nsresult rv =
+      nsContentSecurityManager::doContentSecurityCheck(this, listener);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  MOZ_ASSERT(
+      mLoadInfo->GetSecurityMode() == 0 ||
+          mLoadInfo->GetInitialSecurityCheckDone() ||
+          (mLoadInfo->GetSecurityMode() ==
+               nsILoadInfo::SEC_ALLOW_CROSS_ORIGIN_SEC_CONTEXT_IS_NULL &&
+           mLoadInfo->GetLoadingPrincipal() &&
+           mLoadInfo->GetLoadingPrincipal()->IsSystemPrincipal()),
+      "security flags in loadInfo but doContentSecurityCheck() not called");
+
+  // Double-check that we are actually an icon URL
+  nsCOMPtr<nsIMozIconURI> iconURI(do_QueryInterface(mUrl, &rv));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // Get the handle for the given icon URI. This may involve the decode I/O
+  // thread, as we can only call SHGetFileInfo() from that thread
+  //
+  // Since this API is synchronous, this call will not return until the decode
+  // I/O thread returns with the icon handle
+  //
+  // Once we have the handle, we create a Windows ICO buffer with it and
+  // dump the buffer into the output end of the pipe. The input end will
+  // be returned to the caller
+  HICON hIcon = nullptr;
+  rv = GetIconHandleFromURLBlocking(iconURI, &hIcon);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  ByteBuf iconBuffer;
+  rv = MakeIconBuffer(hIcon, &iconBuffer);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // Create the asynchronous pipe with a blocking read end
+  nsCOMPtr<nsIAsyncInputStream> inputStream;
+  nsCOMPtr<nsIAsyncOutputStream> outputStream;
+  NS_NewPipe2(getter_AddRefs(inputStream), getter_AddRefs(outputStream),
+              false /*nonBlockingInput*/, false /*nonBlockingOutput*/,
+              iconBuffer.mLen /*segmentSize*/, 1 /*segmentCount*/);
+
+  rv = WriteByteBufToOutputStream(iconBuffer, outputStream);
+
+  if (NS_SUCCEEDED(rv)) {
+    inputStream.forget(aStream);
+  }
+
+  return rv;
+}
+
+NS_IMETHODIMP
+nsIconChannel::AsyncOpen(nsIStreamListener* aListener) {
+  nsCOMPtr<nsIStreamListener> listener = aListener;
+  nsresult rv =
+      nsContentSecurityManager::doContentSecurityCheck(this, listener);
+  if (NS_FAILED(rv)) {
+    mCallbacks = nullptr;
+    return rv;
+  }
+
+  MOZ_ASSERT(
+      mLoadInfo->GetSecurityMode() == 0 ||
+          mLoadInfo->GetInitialSecurityCheckDone() ||
+          (mLoadInfo->GetSecurityMode() ==
+               nsILoadInfo::SEC_ALLOW_CROSS_ORIGIN_SEC_CONTEXT_IS_NULL &&
+           mLoadInfo->GetLoadingPrincipal() &&
+           mLoadInfo->GetLoadingPrincipal()->IsSystemPrincipal()),
+      "security flags in loadInfo but doContentSecurityCheck() not called");
+
+  mListener = listener;
+
+  rv = StartAsyncOpen();
+  if (NS_FAILED(rv)) {
+    mListener = nullptr;
+    mCallbacks = nullptr;
+    return rv;
+  }
+
+  // Add ourself to the load group, if available
+  if (mLoadGroup) {
+    mLoadGroup->AddRequest(this, nullptr);
+  }
+
+  return NS_OK;
+}
+
+nsresult nsIconChannel::StartAsyncOpen() {
+  // Double-check that we are actually an icon URL
+  nsresult rv = NS_OK;
+  nsCOMPtr<nsIMozIconURI> iconURI(do_QueryInterface(mUrl, &rv));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // Create the asynchronous pipe with a non-blocking read end
+  nsCOMPtr<nsIAsyncInputStream> inputStream;
+  nsCOMPtr<nsIAsyncOutputStream> outputStream;
+  NS_NewPipe2(getter_AddRefs(inputStream), getter_AddRefs(outputStream),
+              true /*nonBlockingInput*/, false /*nonBlockingOutput*/,
+              0 /*segmentSize*/, UINT32_MAX /*segmentCount*/);
+
+  // If we are in content, we asynchronously request the ICO buffer from
+  // the parent process because the APIs to load icons don't work with
+  // Win32k Lockdown
+  using ContentChild = mozilla::dom::ContentChild;
+  if (auto* contentChild = ContentChild::GetSingleton()) {
+    RefPtr<ContentChild::GetSystemIconPromise> iconPromise =
+        contentChild->SendGetSystemIcon(mUrl);
+    if (!iconPromise) {
+      return NS_ERROR_UNEXPECTED;
+    }
+
+    iconPromise->Then(
+        mozilla::GetCurrentSerialEventTarget(), __func__,
+        [outputStream](std::tuple<nsresult, mozilla::Maybe<ByteBuf>>&& aArg) {
+          nsresult rv = std::get<0>(aArg);
+          mozilla::Maybe<ByteBuf> iconBuffer = std::move(std::get<1>(aArg));
+
+          if (NS_SUCCEEDED(rv)) {
+            MOZ_RELEASE_ASSERT(iconBuffer);
+            rv = WriteByteBufToOutputStream(*iconBuffer, outputStream);
+          }
+
+          outputStream->CloseWithStatus(rv);
+        },
+        [outputStream](mozilla::ipc::ResponseRejectReason) {
+          outputStream->CloseWithStatus(NS_ERROR_FAILURE);
+        });
+  } else {
+    // Get the handle for the given icon URI. This may involve the decode I/O
+    // thread, as we can only call SHGetFileInfo() from that thread
+    //
+    // Once we have the handle, we create a Windows ICO buffer with it and
+    // dump the buffer into the output end of the pipe. The input end will be
+    // pumped to our attached nsIStreamListener
+    GetIconBufferFromURLAsync(iconURI)->Then(
+        GetCurrentSerialEventTarget(), __func__,
+        [outputStream](ByteBuf aIconBuffer) {
+          nsresult rv =
+              WriteByteBufToOutputStream(std::move(aIconBuffer), outputStream);
+          outputStream->CloseWithStatus(rv);
+        },
+        [outputStream](nsresult rv) { outputStream->CloseWithStatus(rv); });
+  }
+
+  // Use the main thread for the pumped events unless the load info
+  // specifies otherwise
+  nsCOMPtr<nsISerialEventTarget> listenerTarget =
+      nsContentUtils::GetEventTargetByLoadInfo(mLoadInfo,
+                                               mozilla::TaskCategory::Other);
+  if (!listenerTarget) {
+    listenerTarget = do_GetMainThread();
+  }
+
+  rv = mPump->Init(inputStream.get(), 0 /*segmentSize*/, 0 /*segmentCount*/,
+                   false /*closeWhenDone*/, listenerTarget);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  return mPump->AsyncRead(this);
+}
+
+NS_IMETHODIMP
+nsIconChannel::GetContentType(nsACString& aContentType) {
+  aContentType.AssignLiteral(IMAGE_ICO);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsIconChannel::SetContentType(const nsACString& aContentType) {
+  // It doesn't make sense to set the content-type on this type
+  // of channel...
+  return NS_ERROR_FAILURE;
+}
+
+NS_IMETHODIMP nsIconChannel::GetContentCharset(nsACString& aContentCharset) {
+  aContentCharset.Truncate();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsIconChannel::SetContentCharset(const nsACString& aContentCharset) {
+  // It doesn't make sense to set the content-charset on this type
+  // of channel...
+  return NS_ERROR_FAILURE;
+}
+
+NS_IMETHODIMP
+nsIconChannel::GetContentDisposition(uint32_t* aContentDisposition) {
+  return NS_ERROR_NOT_AVAILABLE;
+}
+
+NS_IMETHODIMP
+nsIconChannel::SetContentDisposition(uint32_t aContentDisposition) {
+  return NS_ERROR_NOT_AVAILABLE;
+}
+
+NS_IMETHODIMP
+nsIconChannel::GetContentDispositionFilename(
+    nsAString& aContentDispositionFilename) {
+  return NS_ERROR_NOT_AVAILABLE;
+}
+
+NS_IMETHODIMP
+nsIconChannel::SetContentDispositionFilename(
+    const nsAString& aContentDispositionFilename) {
+  return NS_ERROR_NOT_AVAILABLE;
+}
+
+NS_IMETHODIMP
+nsIconChannel::GetContentDispositionHeader(
+    nsACString& aContentDispositionHeader) {
+  return NS_ERROR_NOT_AVAILABLE;
+}
+
+NS_IMETHODIMP
+nsIconChannel::GetContentLength(int64_t* aContentLength) {
+  *aContentLength = 0;
+  return NS_ERROR_FAILURE;
+}
+
+NS_IMETHODIMP
+nsIconChannel::SetContentLength(int64_t aContentLength) {
+  MOZ_ASSERT_UNREACHABLE("nsIconChannel::SetContentLength");
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+nsIconChannel::GetOwner(nsISupports** aOwner) {
+  *aOwner = mOwner.get();
+  NS_IF_ADDREF(*aOwner);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsIconChannel::SetOwner(nsISupports* aOwner) {
+  mOwner = aOwner;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsIconChannel::GetLoadInfo(nsILoadInfo** aLoadInfo) {
+  NS_IF_ADDREF(*aLoadInfo = mLoadInfo);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsIconChannel::SetLoadInfo(nsILoadInfo* aLoadInfo) {
+  MOZ_RELEASE_ASSERT(aLoadInfo, "loadinfo can't be null");
+  mLoadInfo = aLoadInfo;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsIconChannel::GetNotificationCallbacks(
+    nsIInterfaceRequestor** aNotificationCallbacks) {
+  *aNotificationCallbacks = mCallbacks.get();
+  NS_IF_ADDREF(*aNotificationCallbacks);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsIconChannel::SetNotificationCallbacks(
+    nsIInterfaceRequestor* aNotificationCallbacks) {
+  mCallbacks = aNotificationCallbacks;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsIconChannel::GetSecurityInfo(nsITransportSecurityInfo** aSecurityInfo) {
+  *aSecurityInfo = nullptr;
+  return NS_OK;
+}
+
+// nsIRequestObserver methods
+NS_IMETHODIMP nsIconChannel::OnStartRequest(nsIRequest* aRequest) {
+  if (mListener) {
+    return mListener->OnStartRequest(this);
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsIconChannel::OnStopRequest(nsIRequest* aRequest, nsresult aStatus) {
+  if (mListener) {
+    mListener->OnStopRequest(this, aStatus);
+    mListener = nullptr;
+  }
+
+  // Remove from load group
+  if (mLoadGroup) {
+    mLoadGroup->RemoveRequest(this, nullptr, aStatus);
+  }
+
+  // Drop notification callbacks to prevent cycles.
+  mCallbacks = nullptr;
+
+  return NS_OK;
+}
+
+// nsIStreamListener methods
+NS_IMETHODIMP
+nsIconChannel::OnDataAvailable(nsIRequest* aRequest, nsIInputStream* aStream,
+                               uint64_t aOffset, uint32_t aCount) {
+  if (mListener) {
+    return mListener->OnDataAvailable(this, aStream, aOffset, aCount);
+  }
+  return NS_OK;
+}
diff --git a/image/decoders/icon/win/nsIconChannel.h b/image/decoders/icon/win/nsIconChannel.h
new file mode 100644
index 0000000000..4065be76e3
--- /dev/null
+++ b/image/decoders/icon/win/nsIconChannel.h
@@ -0,0 +1,65 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_image_encoders_icon_win_nsIconChannel_h
+#define mozilla_image_encoders_icon_win_nsIconChannel_h
+
+#include "mozilla/Attributes.h"
+#include "mozilla/MozPromise.h"
+
+#include "nsCOMPtr.h"
+#include "nsString.h"
+#include "nsIChannel.h"
+#include "nsILoadGroup.h"
+#include "nsILoadInfo.h"
+#include "nsIInterfaceRequestor.h"
+#include "nsIInterfaceRequestorUtils.h"
+#include "nsIURI.h"
+#include "nsIInputStreamPump.h"
+#include "nsIStreamListener.h"
+
+namespace mozilla::ipc {
+class ByteBuf;
+}
+
+class nsIconChannel final : public nsIChannel, public nsIStreamListener {
+ public:
+  using ByteBufPromise =
+      mozilla::MozPromise<mozilla::ipc::ByteBuf, nsresult, true>;
+
+  NS_DECL_THREADSAFE_ISUPPORTS
+  NS_DECL_NSIREQUEST
+  NS_DECL_NSICHANNEL
+  NS_DECL_NSIREQUESTOBSERVER
+  NS_DECL_NSISTREAMLISTENER
+
+  nsIconChannel();
+
+  nsresult Init(nsIURI* uri);
+
+  /// Obtains an icon in Windows ICO format as a ByteBuf instead
+  /// of a channel. For use with IPC.
+  static RefPtr<ByteBufPromise> GetIconAsync(nsIURI* aURI);
+
+ private:
+  ~nsIconChannel();
+
+  nsresult StartAsyncOpen();
+
+  nsCOMPtr<nsIURI> mUrl;
+  nsCOMPtr<nsIURI> mOriginalURI;
+  nsCOMPtr<nsILoadGroup> mLoadGroup;
+  nsCOMPtr<nsIInterfaceRequestor> mCallbacks;
+  nsCOMPtr<nsISupports> mOwner;
+  nsCOMPtr<nsILoadInfo> mLoadInfo;
+
+  nsCOMPtr<nsIInputStreamPump> mPump;
+  nsCOMPtr<nsIStreamListener> mListener;
+
+  bool mCanceled = false;
+};
+
+#endif  // mozilla_image_encoders_icon_win_nsIconChannel_h