Adjust maximum scroll bounds on FrameView to account for top controls. (Blink-side)

Source/web/WebViewImpl.cpp

Index: Source/web/WebViewImpl.cpp
diff --git a/Source/web/WebViewImpl.cpp b/Source/web/WebViewImpl.cpp
index ed67d3c13a51a80ff78c4f222a4cc9401e4a4ea7..95d534df922d3afb4f64f6f8e8bd8c835b4762fd 100644
--- a/Source/web/WebViewImpl.cpp
+++ b/Source/web/WebViewImpl.cpp
@@ -414,6 +414,7 @@ WebViewImpl::WebViewImpl(WebViewClient* client)
     , m_zoomFactorOverride(0)
     , m_userGestureObserved(false)
     , m_topControlsContentOffset(0)
+    , m_topControlsLayoutHeight(0)
 {
     Page::PageClients pageClients;
     pageClients.chromeClient = &m_chromeClientImpl;
@@ -1666,6 +1667,26 @@ void WebViewImpl::setTopControlsContentOffset(float offset)
 {
     m_topControlsContentOffset = offset;
     m_layerTreeView->setTopControlsContentOffset(offset);
+    didUpdateTopControls();
+}
+
+void WebViewImpl::setTopControlsLayoutHeight(float height)
+{
+    m_topControlsLayoutHeight = height;
+    didUpdateTopControls();
+}
+
+void WebViewImpl::didUpdateTopControls()
+{
+    FrameView* view = localFrameRootTemporary()->frameView();
+    if (!view)
+        return;
+
+    // The viewport bounds were adjusted on the compositor by this much due to top controls. Tell
+    // the FrameView about it so it can make correct scroll offset clamping decisions during compositor
+    // commits.
+    float topControlsViewportAdjustment = m_topControlsContentOffset - m_topControlsLayoutHeight;
+    view->setTopControlsViewportAdjustment(topControlsViewportAdjustment);

[bokan, 2014/09/09 23:14:19]

There's also a Chromium-side patch that just calls setTopControlsLayoutHeight in
RenderWidget::Resize. I'll land this patch first with this line commented out so
it doesn't change behaviour.

[aelias_OOO_until_Jul13, 2014/09/10 01:57:29]

If you prefer, you could also avoid the third patch by making this conditional
on pinch viewport mode being active, as nobody cares about temporary breakage
there yet.

[bokan, 2014/09/10 13:51:52]

One liners like that are easy enough to land + I'd have to change up the test.
Side-note: can I just TBR-commit the patch to uncomment?

[aelias_OOO_until_Jul13, 2014/09/10 15:51:45]

Yes, feel free to TBR that and mention I preapproved that here.

 }
 
 void WebViewImpl::resize(const WebSize& newSize)