1 files changed, 58 insertions, 0 deletions
diff --git a/dom/base/ProcessSelector.sys.mjs b/dom/base/ProcessSelector.sys.mjs
new file mode 100644
index 0000000000..59319f7bf6
--- /dev/null
+++ b/dom/base/ProcessSelector.sys.mjs
@@ -0,0 +1,58 @@
+/* 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/. */
+
+// Fills up aProcesses until max and then selects randomly from the available
+// ones.
+export function RandomSelector() {}
+
+RandomSelector.prototype = {
+  classID: Components.ID("{c616fcfd-9737-41f1-aa74-cee72a38f91b}"),
+  QueryInterface: ChromeUtils.generateQI(["nsIContentProcessProvider"]),
+
+  provideProcess(aType, aProcesses, aMaxCount) {
+    if (aProcesses.length < aMaxCount) {
+      return Ci.nsIContentProcessProvider.NEW_PROCESS;
+    }
+
+    return Math.floor(Math.random() * aMaxCount);
+  },
+};
+
+// Fills up aProcesses until max and then selects one from the available
+// ones that host the least number of tabs.
+export function MinTabSelector() {}
+
+MinTabSelector.prototype = {
+  classID: Components.ID("{2dc08eaf-6eef-4394-b1df-a3a927c1290b}"),
+  QueryInterface: ChromeUtils.generateQI(["nsIContentProcessProvider"]),
+
+  provideProcess(aType, aProcesses, aMaxCount) {
+    let min = Number.MAX_VALUE;
+    let candidate = Ci.nsIContentProcessProvider.NEW_PROCESS;
+
+    // The reason for not directly using aProcesses.length here is because if
+    // we keep processes alive for testing but want a test to use only single
+    // content process we can just keep relying on dom.ipc.processCount = 1
+    // this way.
+    let numIters = Math.min(aProcesses.length, aMaxCount);
+
+    for (let i = 0; i < numIters; i++) {
+      let process = aProcesses[i];
+      let tabCount = process.tabCount;
+      if (tabCount < min) {
+        min = tabCount;
+        candidate = i;
+      }
+    }
+
+    // If all current processes have at least one tab and we have not yet
+    // reached the maximum, spawn a new process.
+    if (min > 0 && aProcesses.length < aMaxCount) {
+      return Ci.nsIContentProcessProvider.NEW_PROCESS;
+    }
+
+    // Otherwise we use candidate.
+    return candidate;
+  },
+};