Mac: Speculative fix for tracking area crashes

ui/base/cocoa/base_view.mm

Index: ui/base/cocoa/base_view.mm
diff --git a/ui/base/cocoa/base_view.mm b/ui/base/cocoa/base_view.mm
index b37b6789435d8a6da2698e72d63b1779adba2957..4d2b6025d3b9e0f211c7fa9f4e3895919bafd626 100644
--- a/ui/base/cocoa/base_view.mm
+++ b/ui/base/cocoa/base_view.mm
@@ -8,20 +8,83 @@ NSString* kViewDidBecomeFirstResponder =
     @"Chromium.kViewDidBecomeFirstResponder";
 NSString* kSelectionDirection = @"Chromium.kSelectionDirection";
 
-const int kTrackingOptions = NSTrackingMouseMoved |
-                             NSTrackingMouseEnteredAndExited |
-                             NSTrackingActiveAlways;
-
 @implementation BaseView
 
+- (instancetype)initWithFrame:(NSRect)frame
+     wantsReliableMouseEvents:(BOOL)wantsReliableMouseEvents {
+  if ((self = [super initWithFrame:frame])) {
+    [self initBaseViewUsingEventTap:wantsReliableMouseEvents];
+  }
+  return self;
+}
+
+- (instancetype)initWithFrame:(NSRect)frame {
+  if ((self = [super initWithFrame:frame])) {
+    [self initBaseViewUsingEventTap:NO];
+  }
+  return self;
+}
+
+- (instancetype)initWithCoder:(NSCoder*)decoder {
+  if ((self = [super initWithCoder:decoder])) {
+    [self initBaseViewUsingEventTap:NO];
+  }
+  return self;
+}
+
+- (void)initBaseViewUsingEventTap:(BOOL)wantsReliableMouseEvents {

[Scott Hess - ex-Googler, 2015/02/27 17:56:11]

IMHO this should not be called -init*, since the caller is handling the -init
chain.  -setupEventTap: maybe?

+  NSTrackingAreaOptions trackingOptions = NSTrackingMouseEnteredAndExited |
+                                          NSTrackingActiveAlways |
+                                          NSTrackingInVisibleRect;
+  if (!wantsReliableMouseEvents)
+    trackingOptions |= NSTrackingMouseMoved;

[Scott Hess - ex-Googler, 2015/02/27 17:56:11]

If this approach is sufficiently performant to use for the web contents, why
even bother having the fallback case?

+  trackingArea_.reset([[CrTrackingArea alloc] initWithRect:NSZeroRect
+                                                   options:trackingOptions
+                                                     owner:self
+                                                  userInfo:nil]);
+  [self addTrackingArea:trackingArea_.get()];
+
+  if (wantsReliableMouseEvents) {
+    // Workaround for http://crbug.com/176725
+    // Check if the mouse moved over us.
+    // Don't do it if we are firstResponder to avoid processing the event twice.
+    eventTap_ = [NSEvent addLocalMonitorForEventsMatchingMask:NSMouseMovedMask
+        handler:^NSEvent*(NSEvent* event) {
+            NSWindow* window = [self window];
+            if (window && window == [event window] &&
+                [window firstResponder] != self) {
+              NSPoint location =
+                  [[self superview] convertPoint:[event locationInWindow]
+                                        fromView:nil];
+              if ([self hitTest:location])
+                [self mouseMoved:event];
+            }
+            return event;
+        }];
+  }
+}
+
 - (void)dealloc {
   if (trackingArea_.get())
     [self removeTrackingArea:trackingArea_.get()];
   trackingArea_.reset(nil);
 
+  if (eventTap_)
+    [NSEvent removeMonitor:eventTap_];
+
   [super dealloc];
 }
 
+- (void)viewDidMoveToWindow {
+  [super viewDidMoveToWindow];
+
+  // Ensure our event tap gets mouse moved events. The mouse moved events are
+  // normally sent to the window's firstResponder (like key events, unlike
+  // other mouse events).
+  if (eventTap_)
+    [[self window] setAcceptsMouseMovedEvents:YES];
+}
+
 - (void)mouseEvent:(NSEvent*)theEvent {
   // This method left intentionally blank.
 }
@@ -138,19 +201,4 @@ const int kTrackingOptions = NSTrackingMouseMoved |
   return new_rect;
 }
 
-- (void)updateTrackingAreas {
-  [super updateTrackingAreas];
-
-  // NSTrackingInVisibleRect doesn't work correctly with Lion's window resizing,
-  // http://crbug.com/176725 / http://openradar.appspot.com/radar?id=2773401 .
-  // Tear down old tracking area and create a new one as workaround.
-  if (trackingArea_.get())
-    [self removeTrackingArea:trackingArea_.get()];
-  trackingArea_.reset([[CrTrackingArea alloc] initWithRect:[self bounds]
-                                                   options:kTrackingOptions
-                                                     owner:self
-                                                  userInfo:nil]);
-  [self addTrackingArea:trackingArea_.get()];
-}
-
 @end