Merge 241918 "mac: Fix a newly introduced history swiping bug."

> mac: Fix a newly introduced history swiping bug.
>
> Attempting to 2-finger history swipe twice in quick succession would
> fail to register the second swipe ~50% of the time. The NSEvent callback with
> phase=NSEventPhaseBegan non-deterministically occurs before the event has been
> registered as a gesture. This was causing the history_swiper to process the
> event as part of the previous gesture.
>
> BUG=138175
> TEST=In a single tab, navigate to 5 different sites. Use a trackpad to 2-finger
> swipe repeatedly in the same direction. Each swipe should register as a history
> swipe, and cause the page to navigate in the appropriate direction. There
> should be no jankiness, and the touches should not fail to register.
>
> Review URL: https://codereview.chromium.org/117733002

TBR=erikchen@chromium.org

Review URL: https://codereview.chromium.org/132693021

git-svn-id: svn://svn.chromium.org/chrome/branches/1750/src@246367 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 34 insertions, 0 deletions

diff --git a/base/mac/sdk_forward_declarations.h b/base/mac/sdk_forward_declarations.h
index c2383f8..bbaf962 100644
--- a/base/mac/sdk_forward_declarations.h
+++ b/base/mac/sdk_forward_declarations.h
@@ -22,6 +22,7 @@ enum {
   NSEventPhaseChanged     = 0x1 << 2,
   NSEventPhaseEnded       = 0x1 << 3,
   NSEventPhaseCancelled   = 0x1 << 4,
+  NSEventPhaseMayBegin    = 0x1 << 5
 };
 typedef NSUInteger NSEventPhase;
 
diff --git a/chrome/browser/renderer_host/chrome_render_widget_host_view_mac_history_swiper.mm b/chrome/browser/renderer_host/chrome_render_widget_host_view_mac_history_swiper.mm
index 08c758e..d96a154 100644
--- a/chrome/browser/renderer_host/chrome_render_widget_host_view_mac_history_swiper.mm
+++ b/chrome/browser/renderer_host/chrome_render_widget_host_view_mac_history_swiper.mm
@@ -282,9 +282,18 @@
 - (BOOL)maybeHandleHistorySwiping:(NSEvent*)theEvent {
   // We've already processed this gesture.
   if (lastProcessedGestureId_ == currentGestureId_) {
+    // A new event may come in before it's recognized as a gesture.
+    // We have not yet reset the state from the last gesture.
+    // Let it pass through.
+    if ([theEvent phase] == NSEventPhaseBegan ||
+        [theEvent phase] == NSEventPhaseMayBegin) {
+      return NO;
+    }
+
     // The user cancelled the history swiper. Ignore all events.
     if (historySwipeCancelled_)
       return NO;
+
     // The user completed the history swiper. Swallow all events.
     return YES;
   }
diff --git a/chrome/browser/renderer_host/chrome_render_widget_host_view_mac_history_swiper_unit_test.mm b/chrome/browser/renderer_host/chrome_render_widget_host_view_mac_history_swiper_unit_test.mm
index bd2d382..2e0c3ba 100644
--- a/chrome/browser/renderer_host/chrome_render_widget_host_view_mac_history_swiper_unit_test.mm
+++ b/chrome/browser/renderer_host/chrome_render_widget_host_view_mac_history_swiper_unit_test.mm
@@ -328,3 +328,27 @@ TEST_F(MacHistorySwiperTest, NoSwipe) {
   EXPECT_EQ(begin_count_, 0);
   EXPECT_EQ(end_count_, 0);
 }
+
+// After a gesture is successfully recognized, momentum events should be
+// swallowed, but new events should pass through.
+TEST_F(MacHistorySwiperTest, TouchEventAfterGestureFinishes) {
+  // These tests require 10.7+ APIs.
+  if (![NSEvent
+          respondsToSelector:@selector(isSwipeTrackingFromScrollEventsEnabled)])
+    return;
+
+  // Successfully pass through a gesture.
+  startGestureInMiddle();
+  moveGestureInMiddle();
+  moveGestureAtPoint(makePoint(0.8, 0.5));
+  endGestureAtPoint(makePoint(0.8, 0.5));
+  EXPECT_TRUE(navigated_right_);
+
+  // Momentum events should be swallowed.
+  NSEvent* momentumEvent = scrollWheelEventWithPhase(NSEventPhaseNone);
+  EXPECT_TRUE([historySwiper_ handleEvent:momentumEvent]);
+
+  // New events should not be swallowed.
+  NSEvent* beganEvent = scrollWheelEventWithPhase(NSEventPhaseBegan);
+  EXPECT_FALSE([historySwiper_ handleEvent:beganEvent]);
+}