Switch AccessibilityMode to be a bitmap

content/browser/accessibility/browser_accessibility_state_impl.h

Index: content/browser/accessibility/browser_accessibility_state_impl.h
diff --git a/content/browser/accessibility/browser_accessibility_state_impl.h b/content/browser/accessibility/browser_accessibility_state_impl.h
index 3098341ef25efeb46fef8762a7e1d3512e5fad86..0e712584727273ee6d8ee994914f142c8994bf41 100644
--- a/content/browser/accessibility/browser_accessibility_state_impl.h
+++ b/content/browser/accessibility/browser_accessibility_state_impl.h
@@ -48,8 +48,16 @@ class CONTENT_EXPORT BrowserAccessibilityStateImpl
 
   virtual void UpdateHistogramsForTesting() OVERRIDE;
 
-  AccessibilityMode accessibility_mode() const { return accessibility_mode_; };
-  void SetAccessibilityMode(AccessibilityMode mode);
+  unsigned int accessibility_mode() const { return accessibility_mode_; };
+
+  // Adds the given accessibility mode to the current accessibility mode bitmap.
+  void AddAccessibilityMode(AccessibilityMode mode);
+
+  // Removes the given accessibility mode from the current accessibility mode
+  // bitmap, managing the bits that are shared with other modes such that a
+  // bit will only be turned off when all modes that depend on it have been
+  // removed.
+  void RemoveAccessibilityMode(AccessibilityMode mode);
 
  private:
   friend class base::RefCountedThreadSafe<BrowserAccessibilityStateImpl>;
@@ -64,7 +72,11 @@ class CONTENT_EXPORT BrowserAccessibilityStateImpl
 
   void UpdatePlatformSpecificHistograms();
 
-  AccessibilityMode accessibility_mode_;
+  // Updates the accessibility mode of all render widgets, including swapped out
+  // ones. |add| specifies whether the mode should be added or removed.
+  void AddOrRemoveFromRenderWidgets(AccessibilityMode mode, bool add);
+
+  unsigned int accessibility_mode_;
 
   std::vector<base::Closure> histogram_callbacks_;