Squelch context menus on the OSX App List when both buttons are pressed.

The apps grid uses [NSView menuForEvent:..] for its menus, so needs to
check the button state explicitly to match the behaviour of [NSButton
menu] (which isn't used, e.g., because the NSButton doesn't fill the
grid cell).

This CL adds a check to suppress the menu when the button is in the
"lit" state, which occurs when the button is being held down.

BUG=328835
TEST=Hold the left, then the right, mouse buttons over a app launcher
item. A menu shouldn't appear. Releasing the left button (without moving
the mouse cursor) will launch the item.

Review URL: https://codereview.chromium.org/93793012

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@243391 0039d316-1c4b-4281-b951-d872f2087c98

ui/app_list/cocoa/apps_grid_controller_unittest.mm

@@ -983,6 +983,13 @@ TEST_F(AppsGridControllerTest, ContextMenus) {
   menu = [page menuForEvent:mouse_at_cell_1];
   EXPECT_EQ(1, [menu numberOfItems]);
   EXPECT_NSEQ(@"Menu For: Item Two", [[menu itemAtIndex:0] title]);
+
+  // Test that a button being held down with the left button does not also show
+  // a context menu.
+  [GetItemViewAt(0) highlight:YES];
+  EXPECT_FALSE([page menuForEvent:mouse_at_cell_0]);
+  [GetItemViewAt(0) highlight:NO];
+  EXPECT_TRUE([page menuForEvent:mouse_at_cell_0]);
 }
 
 }  // namespace test

ui/app_list/cocoa/apps_grid_view_item.mm

@@ -345,6 +345,10 @@ void ItemModelObserverBridge::ItemPercentDownloadedChanged() {
 }
 
 - (NSMenu*)contextMenu {
+  // Don't show the menu if button is already held down, e.g. with a left-click.
+  if ([[[self button] cell] isHighlighted])
+    return nil;
+
   [self setSelected:YES];
   return observerBridge_->GetContextMenu();
 }