Bug 1540694 - Fix DEBUG_DEVTOOLS_ALLOCATIONS now that DevTools share the unique system compartment. r=jdescottes

In bug 1517210, DevTools started sharing the same compartment than JSMs.
So we can no longer use a Debugger instance bound to jsdebugger.jsm as it
would run in the same compartment than DevTools code we want to inspect
from the allocation tracker.
Instead, we instantiate the Debugger from a custom Sandbox loaded
in a unique and distinct compartment.

Depends on D26077

Differential Revision: https://phabricator.services.mozilla.com/D26078

--HG--
extra : moz-landing-system : lando

devtools/client/shared/test/shared-head.js

@@ -12,6 +12,30 @@
 
 const { Constructor: CC } = Components;
 
+// Print allocation count if DEBUG_DEVTOOLS_ALLOCATIONS is set to "normal",
+// and allocation sites if DEBUG_DEVTOOLS_ALLOCATIONS is set to "verbose".
+const env = Cc["@mozilla.org/process/environment;1"].getService(Ci.nsIEnvironment);
+const DEBUG_ALLOCATIONS = env.get("DEBUG_DEVTOOLS_ALLOCATIONS");
+if (DEBUG_ALLOCATIONS) {
+  // Use a custom loader with `invisibleToDebugger` flag for the allocation tracker
+  // as it instantiates custom Debugger API instances and has to be running in a distinct
+  // compartments from DevTools and system scopes (JSMs, XPCOM,...)
+  const { DevToolsLoader } = ChromeUtils.import("resource://devtools/shared/Loader.jsm");
+  const loader = new DevToolsLoader();
+  loader.invisibleToDebugger = true;
+
+  const { allocationTracker } = loader.require("devtools/shared/test-helpers/allocation-tracker");
+  const tracker = allocationTracker();
+  registerCleanupFunction(() => {
+    if (DEBUG_ALLOCATIONS == "normal") {
+      tracker.logCount();
+    } else if (DEBUG_ALLOCATIONS == "verbose") {
+      tracker.logAllocationSites();
+    }
+    tracker.stop();
+  });
+}
+
 function scopedCuImport(path) {
   const scope = {};
   ChromeUtils.import(path, scope);
@@ -91,23 +115,6 @@ registerCleanupFunction(() => {
   Services.obs.removeObserver(ConsoleObserver, "console-api-log-event");
 });
 
-// Print allocation count if DEBUG_DEVTOOLS_ALLOCATIONS is set to "normal",
-// and allocation sites if DEBUG_DEVTOOLS_ALLOCATIONS is set to "verbose".
-const env = Cc["@mozilla.org/process/environment;1"].getService(Ci.nsIEnvironment);
-const DEBUG_ALLOCATIONS = env.get("DEBUG_DEVTOOLS_ALLOCATIONS");
-if (DEBUG_ALLOCATIONS) {
-  const { allocationTracker } = require("devtools/shared/test-helpers/allocation-tracker");
-  const tracker = allocationTracker();
-  registerCleanupFunction(() => {
-    if (DEBUG_ALLOCATIONS == "normal") {
-      tracker.logCount();
-    } else if (DEBUG_ALLOCATIONS == "verbose") {
-      tracker.logAllocationSites();
-    }
-    tracker.stop();
-  });
-}
-
 var waitForTime = DevToolsUtils.waitForTime;
 
 function loadFrameScriptUtils(browser = gBrowser.selectedBrowser) {

devtools/shared/test-helpers/allocation-tracker.js

@@ -36,17 +36,15 @@
 "use strict";
 
 const { Cu } = require("chrome");
+const ChromeUtils = require("ChromeUtils");
 
-// Get a "Debugger" constructor. Can't call `addDebuggerToGlobal`
-// on the frame script global, so call it on jsdebugger one...
-const global = require("resource://gre/modules/jsdebugger.jsm");
-const {addDebuggerToGlobal} = global;
+const global = Cu.getGlobalForObject(this);
+const {addDebuggerToGlobal} = ChromeUtils.import("resource://gre/modules/jsdebugger.jsm");
 addDebuggerToGlobal(global);
-const { Debugger } = global;
 
 exports.allocationTracker = function() {
   dump("DEVTOOLS ALLOCATION: Start logging allocations\n");
-  let dbg = new Debugger();
+  let dbg = new global.Debugger();
 
   // Enable allocation site tracking, to have the stack for each allocation
   dbg.memory.trackingAllocationSites = true;
@@ -59,7 +57,7 @@ exports.allocationTracker = function() {
   dbg.addAllGlobalsAsDebuggees();
 
   // Remove this global to ignore all its object/JS
-  dbg.removeDebuggee(Cu.getGlobalForObject({}));
+  dbg.removeDebuggee(global);
 
   // addAllGlobalsAsDebuggees won't automatically track new ones,
   // so ensure tracking all new globals