Send early ShowPress on TapDown when page isn't scrollable/pinchable.

Source/web/WebViewImpl.cpp

Index: Source/web/WebViewImpl.cpp
diff --git a/Source/web/WebViewImpl.cpp b/Source/web/WebViewImpl.cpp
index 5e2f87550859c5fc9913fc9a98807e382af7de04..3f6e5cb828dea0945983ecde15b60db01d8b9ac3 100644
--- a/Source/web/WebViewImpl.cpp
+++ b/Source/web/WebViewImpl.cpp
@@ -375,6 +375,7 @@ WebViewImpl::WebViewImpl(WebViewClient* client)
     , m_baseBackgroundColor(Color::white)
     , m_backgroundColorOverride(Color::transparent)
     , m_zoomFactorOverride(0)
+    , m_sentEarlyShowPress(false)
 {
     Page::PageClients pageClients;
     pageClients.chromeClient = &m_chromeClientImpl;
@@ -630,6 +631,10 @@ bool WebViewImpl::handleGestureEvent(const WebGestureEvent& event)
     // complicated set of cases handled below.
     switch (event.type) {
     case WebInputEvent::GestureShowPress:
+        // Skip if already seen a ShowPress triggered by TapDown.
+        if (m_sentEarlyShowPress)
+            return false;
+
         // Queue a highlight animation, then hand off to regular handler.
         if (settingsImpl()->gestureTapHighlightEnabled())
             enableTapHighlightAtPoint(platformEvent);
@@ -724,10 +729,13 @@ bool WebViewImpl::handleGestureEvent(const WebGestureEvent& event)
         // GestureTap with tap count = 2 is used instead. So we drop GestureDoubleTap here.
         eventSwallowed = true;
         break;
+    case WebInputEvent::GestureTapDown:
+        m_sentEarlyShowPress = false;
+        eventSwallowed = mainFrameImpl()->frame()->eventHandler().handleGestureEvent(platformEvent);
+        break;
     case WebInputEvent::GestureScrollBegin:
     case WebInputEvent::GesturePinchBegin:
         m_client->cancelScheduledContentIntents();
-    case WebInputEvent::GestureTapDown:
     case WebInputEvent::GestureScrollEnd:
     case WebInputEvent::GestureScrollUpdate:
     case WebInputEvent::GestureScrollUpdateWithoutPropagation:
@@ -743,9 +751,40 @@ bool WebViewImpl::handleGestureEvent(const WebGestureEvent& event)
         ASSERT_NOT_REACHED();
     }
     m_client->didHandleGestureEvent(event, eventCancelled);
+
+    if (event.type == WebInputEvent::GestureTapDown
+        && earlyGestureShowPress(platformEvent)) {
+        WebGestureEvent showPressEvent = event;
+        showPressEvent.type = WebInputEvent::GestureShowPress;
+        eventSwallowed = handleGestureEvent(showPressEvent);
+        // Ignore subsequent ShowPress events until another TapDown
+        m_sentEarlyShowPress = true;
+    }
+
     return eventSwallowed;
 }
 
+// GestureShowPress is normally delayed to avoid triggering on the start of a
+// scroll, but when scrolling and pinching aren't possible we can do the
+// ShowPress early, immediately after TapDown.
+bool WebViewImpl::earlyGestureShowPress(const WebCore::PlatformGestureEvent& event)
+{
+    LocalFrame* mainFrame = mainFrameImpl()->frame();
+    FrameView* frameView = mainFrame->view();
+
+    if (frameView && !frameView->isScrollable() && !isPinchZoomable()) {
+        IntPoint adjustedPoint = event.position();
+        LocalFrame* eventFrame = mainFrame->eventHandler().frameForGestureEvent(event, adjustedPoint);
+        IntPoint hitTestPoint = eventFrame->view()->windowToContents(event.position());
+        HitTestResult result = eventFrame->eventHandler().hitTestResultAtPoint(hitTestPoint, HitTestRequest::TouchEvent | HitTestRequest::ReadOnly  | HitTestRequest::AllowFrameScrollbars);
+
+        // If no ancestor is scrollable then this couldn't possibly be the start of a scroll.
+        return !eventFrame->eventHandler().hasScrollableAncestor(result.innerElement());
+    }
+
+    return false;
+}
+
 void WebViewImpl::transferActiveWheelFlingAnimation(const WebActiveWheelFlingParameters& parameters)
 {
     TRACE_EVENT0("webkit", "WebViewImpl::transferActiveWheelFlingAnimation");
@@ -2913,6 +2952,15 @@ float WebViewImpl::maximumPageScaleFactor() const
     return m_pageScaleConstraintsSet.finalConstraints().maximumScale;
 }
 
+bool WebViewImpl::isPinchZoomable() const
+{
+    // This covers all cases:
+    //  * viewport user-scalable: no
+    //  * viewport minimum and maximum scale equal
+    //  * pinch disabled by command line flag
+    return minimumPageScaleFactor() != maximumPageScaleFactor();
+}
+
 void WebViewImpl::saveScrollAndScaleState()
 {
     m_savedPageScaleFactor = pageScaleFactor();