Add an accessibility API for events raised outside of the web content.

chrome/browser/profile.h

Index: chrome/browser/profile.h
===================================================================
--- chrome/browser/profile.h	(revision 37511)
+++ chrome/browser/profile.h	(working copy)
@@ -103,7 +103,7 @@
   // Value that represents no profile Id.
   static const ProfileId InvalidProfileId;
 
-  Profile() : restored_last_session_(false) {}
+  Profile() : restored_last_session_(false), accessibility_pause_level_(0) {}
   virtual ~Profile() {}
 
   // Profile prefs are registered as soon as the prefs are loaded for the first
@@ -385,11 +385,33 @@
     return restored_last_session_;
   }
 
+  // Stop sending accessibility events until ResumeAccessibilityEvents().
+  // Calls to Pause nest; no events will be sent until the number of
+  // Resume calls matches the number of Pause calls received.
+  void PauseAccessibilityEvents() {
+    accessibility_pause_level_++;
+  }
+
+  void ResumeAccessibilityEvents() {
+    DCHECK(accessibility_pause_level_ > 0);
+    accessibility_pause_level_--;
+  }
+
+  bool ShouldSendAccessibilityEvents() {
+    return 0 == accessibility_pause_level_;
+  }
+
  protected:
   static URLRequestContextGetter* default_request_context_;
 
  private:
   bool restored_last_session_;
+
+  // Accessibility events will only be propagated when the pause
+  // level is zero.  PauseAccessibilityEvents and ResumeAccessibilityEvents
+  // increment and decrement the level, respectively, rather than set it to
+  // true or false, so that calls can be nested.
+  int accessibility_pause_level_;
 };
 
 class OffTheRecordProfileImpl;