Fixes for nonmodal pinch zoom.

In Android 4.2, pinch gestures send both pinch events (for the
zoom-in/out part of the pinch) and scroll events (for double-finger
panning).  The previous logic in LayerTreeHostImpl created a pan from
the pinch event, resulting in 2x overpanning on Android 4.2.

In order to have compatible gesture generation in older Android versions as
well, I copy-pasted the latest Android GestureDetector.java file into the
Chromium tree and use that instead of the system file.

BUG=161909

Review URL: https://chromiumcodereview.appspot.com/11299083

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@168721 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 23 insertions, 5 deletions

diff --git a/cc/layer_tree_host_impl.cc b/cc/layer_tree_host_impl.cc
index 8c2df3c..8ea79c2 100644
--- a/cc/layer_tree_host_impl.cc
+++ b/cc/layer_tree_host_impl.cc
@@ -1241,13 +1241,10 @@ void LayerTreeHostImpl::pinchGestureUpdate(float magnifyDelta, gfx::Point anchor
     if (!m_rootScrollLayerImpl)
         return;
 
-    if (m_previousPinchAnchor == gfx::Point())
-        m_previousPinchAnchor = anchor;
-
     // Keep the center-of-pinch anchor specified by (x, y) in a stable
     // position over the course of the magnify.
     float pageScaleDelta = m_pinchZoomViewport.pageScaleDelta();
-    gfx::PointF previousScaleAnchor = gfx::ScalePoint(m_previousPinchAnchor, 1 / pageScaleDelta);
+    gfx::PointF previousScaleAnchor = gfx::ScalePoint(anchor, 1 / pageScaleDelta);
     setPageScaleDelta(pageScaleDelta * magnifyDelta);
     pageScaleDelta = m_pinchZoomViewport.pageScaleDelta();
     gfx::PointF newScaleAnchor = gfx::ScalePoint(anchor, 1 / pageScaleDelta);
diff --git a/cc/layer_tree_host_impl_unittest.cc b/cc/layer_tree_host_impl_unittest.cc
index 278f467..f772155 100644
--- a/cc/layer_tree_host_impl_unittest.cc
+++ b/cc/layer_tree_host_impl_unittest.cc
@@ -646,7 +646,7 @@ TEST_P(LayerTreeHostImplTest, pinchGesture)
         }
     }
 
-    // Two-finger panning
+    // Two-finger panning should not happen based on pinch events only
     {
         m_hostImpl->setPageScaleFactorAndLimits(1, minPageScale, maxPageScale);
         scrollLayer->setImplTransform(identityScaleTransform);
@@ -661,6 +661,27 @@ TEST_P(LayerTreeHostImplTest, pinchGesture)
 
         scoped_ptr<ScrollAndScaleSet> scrollInfo = m_hostImpl->processScrollDeltas();
         EXPECT_EQ(scrollInfo->pageScaleDelta, pageScaleDelta);
+        EXPECT_TRUE(scrollInfo->scrolls.empty());
+    }
+
+    // Two-finger panning should work with interleaved scroll events
+    {
+        m_hostImpl->setPageScaleFactorAndLimits(1, minPageScale, maxPageScale);
+        scrollLayer->setImplTransform(identityScaleTransform);
+        scrollLayer->setScrollDelta(gfx::Vector2d());
+        scrollLayer->setScrollOffset(gfx::Vector2d(20, 20));
+
+        float pageScaleDelta = 1;
+        m_hostImpl->scrollBegin(gfx::Point(10, 10), InputHandlerClient::Wheel);
+        m_hostImpl->pinchGestureBegin();
+        m_hostImpl->pinchGestureUpdate(pageScaleDelta, gfx::Point(10, 10));
+        m_hostImpl->scrollBy(gfx::Point(10, 10), gfx::Vector2d(-10, -10));
+        m_hostImpl->pinchGestureUpdate(pageScaleDelta, gfx::Point(20, 20));
+        m_hostImpl->pinchGestureEnd();
+        m_hostImpl->scrollEnd();
+
+        scoped_ptr<ScrollAndScaleSet> scrollInfo = m_hostImpl->processScrollDeltas();
+        EXPECT_EQ(scrollInfo->pageScaleDelta, pageScaleDelta);
         expectContains(*scrollInfo, scrollLayer->id(), gfx::Vector2d(-10, -10));
     }
 }