Implement top controls show/hide functionality for main thread scrolling

Source/web/WebViewImpl.h

Index: Source/web/WebViewImpl.h
diff --git a/Source/web/WebViewImpl.h b/Source/web/WebViewImpl.h
index 70896b71787c276cb6bcbd6633204d8511a97c80..ebdc6ea54b2c2885862d788cdb1972d9cfc8b73b 100644
--- a/Source/web/WebViewImpl.h
+++ b/Source/web/WebViewImpl.h
@@ -60,6 +60,7 @@
 #include "web/PageWidgetDelegate.h"
 #include "web/SpellCheckerClientImpl.h"
 #include "web/StorageClientImpl.h"
+#include "web/TopControls.h"
 #include "wtf/OwnPtr.h"
 #include "wtf/RefCounted.h"
 #include "wtf/Vector.h"
@@ -517,15 +518,21 @@ public:
     bool matchesHeuristicsForGpuRasterizationForTesting() const { return m_matchesHeuristicsForGpuRasterization; }
 
     virtual void setTopControlsHeight(float height, bool topControlsShrinkLayoutSize) override;
+    virtual void updateTopControlsState(WebTopControlsState constraint, WebTopControlsState current, bool animate) override;
+
+    // Exposed for tests.
+    TopControls* topControls() { return m_topControls.get(); }
+    // Called anytime top controls layout height or content offset have changed.
+    void didUpdateTopControls();
+    // Called by top controls manager to determine if top controls should scroll.
+    bool shouldTopControlsConsumeScroll(float scrollDeltaY);
 
     virtual void forceNextWebGLContextCreationToFail() override;
 
     IntSize mainFrameSize();
 
 private:
-    void didUpdateTopControls();
     void setTopControlsShownRatio(float);
-
     // TODO(bokan): Remains for legacy pinch. Remove once it's gone. Made private to
     // prevent external usage
     virtual void setPageScaleFactor(float scaleFactor, const WebPoint& origin) override;
@@ -757,14 +764,7 @@ private:
 
     bool m_userGestureObserved;
 
-    // The top controls shown amount (normalized from 0 to 1) since the last
-    // compositor commit.
-    float m_topControlsShownRatio;
-
-    float m_topControlsHeight;
-    // If this is true, then the embedder shrunk the WebView size by the top
-    // controls height.
-    bool m_topControlsShrinkLayoutSize;
+    OwnPtr<TopControls> m_topControls;

[aelias_OOO_until_Jul13, 2015/02/13 02:03:17]

The lifetime is identical to WebViewImpl, so let's make this just a regular
member field.

[majidvp, 2015/02/18 21:03:57]

Done. Moved it inside FrameHost and made it a regular member.

 };
 
 DEFINE_TYPE_CASTS(WebViewImpl, WebWidget, widget, widget->isWebView(), widget.isWebView());