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diff --git a/js/public/experimental/CompileScript.h b/js/public/experimental/CompileScript.h
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 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/. */
+
+/* JavaScript API for compiling scripts to stencil without depending on
+ * JSContext. */
+
+#ifndef js_experimental_CompileScript_h
+#define js_experimental_CompileScript_h
+
+#include "jspubtd.h"
+#include "js/experimental/JSStencil.h"
+#include "js/GCAnnotations.h"
+#include "js/Modules.h"
+#include "js/Stack.h"
+#include "js/UniquePtr.h"
+
+namespace js {
+class FrontendContext;
+namespace frontend {
+struct CompilationInput;
+}  // namespace frontend
+}  // namespace js
+
+namespace JS {
+using FrontendContext = js::FrontendContext;
+
+// Create a new front-end context.
+JS_PUBLIC_API JS::FrontendContext* NewFrontendContext();
+
+// Destroy a front-end context allocated with NewFrontendContext.
+JS_PUBLIC_API void DestroyFrontendContext(JS::FrontendContext* fc);
+
+JS_PUBLIC_API void SetNativeStackQuota(JS::FrontendContext* fc,
+                                       JS::NativeStackSize stackSize);
+
+/*
+ * Set supported import assertions on a FrontendContext to be used with
+ * CompileModuleScriptToStencil. May only be set once for each FrontendContext.
+ * The default list of supported import assertions is empty.
+ */
+JS_PUBLIC_API bool SetSupportedImportAssertions(
+    JS::FrontendContext* fc,
+    const JS::ImportAssertionVector& supportedImportAssertions);
+
+// Temporary storage used during compiling and preparing to instantiate a
+// Stencil.
+//
+// Off-thread consumers can allocate this instance off main thread, and pass it
+// back to the main thread, in order to reduce the main thread allocation.
+struct CompilationStorage {
+ private:
+  // Owned CompilationInput.
+  //
+  // This uses raw pointer instead of UniquePtr because CompilationInput
+  // is opaque.
+  JS_HAZ_NON_GC_POINTER js::frontend::CompilationInput* input_ = nullptr;
+  bool isBorrowed_ = false;
+
+ public:
+  CompilationStorage() = default;
+  explicit CompilationStorage(js::frontend::CompilationInput* input)
+      : input_(input), isBorrowed_(true) {}
+  CompilationStorage(CompilationStorage&& other)
+      : input_(other.input_), isBorrowed_(other.isBorrowed_) {
+    other.input_ = nullptr;
+  }
+
+  ~CompilationStorage();
+
+ private:
+  CompilationStorage(const CompilationStorage& other) = delete;
+  void operator=(const CompilationStorage& aOther) = delete;
+
+ public:
+  bool hasInput() { return !!input_; }
+
+  // Internal function that initializes the CompilationInput. It should only be
+  // called once.
+  bool allocateInput(FrontendContext* fc,
+                     const JS::ReadOnlyCompileOptions& options);
+
+  js::frontend::CompilationInput& getInput() {
+    MOZ_ASSERT(hasInput());
+    return *input_;
+  }
+
+  // Size of dynamic data. Note that GC data is counted by GC and not here.
+  size_t sizeOfIncludingThis(mozilla::MallocSizeOf mallocSizeOf) const;
+
+  void trace(JSTracer* trc);
+};
+
+extern JS_PUBLIC_API already_AddRefed<JS::Stencil> CompileGlobalScriptToStencil(
+    JS::FrontendContext* fc, const JS::ReadOnlyCompileOptions& options,
+    JS::SourceText<mozilla::Utf8Unit>& srcBuf,
+    JS::CompilationStorage& compileStorage);
+
+extern JS_PUBLIC_API already_AddRefed<JS::Stencil> CompileGlobalScriptToStencil(
+    JS::FrontendContext* fc, const JS::ReadOnlyCompileOptions& options,
+    JS::SourceText<char16_t>& srcBuf, JS::CompilationStorage& compileStorage);
+
+extern JS_PUBLIC_API already_AddRefed<JS::Stencil> CompileModuleScriptToStencil(
+    JS::FrontendContext* fc, const JS::ReadOnlyCompileOptions& options,
+    JS::SourceText<mozilla::Utf8Unit>& srcBuf,
+    JS::CompilationStorage& compileStorage);
+
+extern JS_PUBLIC_API already_AddRefed<JS::Stencil> CompileModuleScriptToStencil(
+    JS::FrontendContext* fc, const JS::ReadOnlyCompileOptions& options,
+    JS::SourceText<char16_t>& srcBuf, JS::CompilationStorage& compileStorage);
+
+extern JS_PUBLIC_API bool PrepareForInstantiate(
+    JS::FrontendContext* fc, JS::CompilationStorage& compileStorage,
+    JS::Stencil& stencil, JS::InstantiationStorage& storage);
+
+}  // namespace JS
+
+#endif  // js_experimental_CompileScript_h