Fix bug that causes spurious tab switches.

chrome/browser/ui/cocoa/tabs/tab_view.mm

Index: chrome/browser/ui/cocoa/tabs/tab_view.mm
diff --git a/chrome/browser/ui/cocoa/tabs/tab_view.mm b/chrome/browser/ui/cocoa/tabs/tab_view.mm
index 45f042013cd4c9b18d629a8d4f8176810d1b274c..05da4d9060455c966d60edba1320898e02a26db1 100644
--- a/chrome/browser/ui/cocoa/tabs/tab_view.mm
+++ b/chrome/browser/ui/cocoa/tabs/tab_view.mm
@@ -47,10 +47,6 @@ const NSTimeInterval kAlertHideDuration = 0.4;
 // increasing/decreasing).
 const NSTimeInterval kGlowUpdateInterval = 0.025;
 
-// This is used to judge whether the mouse has moved during rapid closure; if it
-// has moved less than the threshold, we want to close the tab.
-const CGFloat kRapidCloseDist = 2.5;
-
 // This class contains the logic for drawing Material Design tab images. The
 // |setTabEdgeStrokeColor| method is overridden by |TabHeavyImageMaker| to draw
 // high-contrast tabs.
@@ -344,37 +340,13 @@ CGFloat LineWidthFromContext(CGContextRef context) {
 }
 
 - (void)mouseUp:(NSEvent*)theEvent {
-  // Check for rapid tab closure.
-  if ([theEvent type] == NSLeftMouseUp) {
-    NSPoint upLocation = [theEvent locationInWindow];
-    CGFloat dx = upLocation.x - mouseDownPoint_.x;
-    CGFloat dy = upLocation.y - mouseDownPoint_.y;
-
-    // During rapid tab closure (mashing tab close buttons), we may get hit

[Robert Sesek, 2016/09/08 15:15:12]

Why is this no longer necesary?

[erikchen, 2016/09/08 17:09:46]

Whoops, still needed.

-    // with a mouse down. As long as the mouse up is over the close button,
-    // and the mouse hasn't moved too much, we close the tab.
-    if (![closeButton_ isHidden] &&
-        (dx*dx + dy*dy) <= kRapidCloseDist*kRapidCloseDist &&
-        [controller_ inRapidClosureMode]) {
-      NSPoint hitLocation =
-          [[self superview] convertPoint:[theEvent locationInWindow]
-                                fromView:nil];
-      if ([self hitTest:hitLocation] == closeButton_) {
-        [controller_ closeTab:self];
-        return;
-      }
-    }
-  }
-
-  // Fire the action to select the tab.
-  [controller_ selectTab:self];

[Robert Sesek, 2016/09/08 15:15:12]

This is no longer necessary because the super triggers the cell's target-action?
(Or the custom loop in -[TabStripDragController maybeStartDrag:forTab:] does
it).

[erikchen, 2016/09/08 17:09:46]

The nested run loop in -[TabStripDragController maybeStartDrag:forTab:]
processes the mouseUp: event. This code is never called.

-
-  // Messaging the drag controller with |-endDrag:| would seem like the right
-  // thing to do here. But, when a tab has been detached, the controller's
-  // target is nil until the drag is finalized. Since |-mouseUp:| gets called
-  // via the manual event loop inside -[TabStripDragController
-  // maybeStartDrag:forTab:], the drag controller can end the dragging session
-  // itself directly after calling this.
+  // This method intentionally forwards to the super implementation without
+  // doing anything. mouseDown: triggers a nested run loop that swallows the
+  // mouseUp: event, so we never expect a meaningful mouseUp: on a TabView.
+  // There's a bug in AppKit that triggers mouseUp: callbacks on inappropriate
+  // views, so it's doubly important that this method doesn't do anything.
+  // https://crbug.com/511095.
+  [super mouseUp:theEvent];
 }
 
 - (void)otherMouseUp:(NSEvent*)theEvent {