Normalize top controls offset to (0, 1), Blink-side.

Source/web/WebViewImpl.cpp

Index: Source/web/WebViewImpl.cpp
diff --git a/Source/web/WebViewImpl.cpp b/Source/web/WebViewImpl.cpp
index 06e1c3efd3a9d6a137123b869811287b1502407b..5112ad5cacdb515248cd5ebbc9375bcb4c802816 100644
--- a/Source/web/WebViewImpl.cpp
+++ b/Source/web/WebViewImpl.cpp
@@ -413,7 +413,9 @@ WebViewImpl::WebViewImpl(WebViewClient* client)
     , m_zoomFactorOverride(0)
     , m_userGestureObserved(false)
     , m_topControlsContentOffset(0)
-    , m_topControlsLayoutHeight(0)
+    , m_topControlsHeight(0)
+    , m_topControlsShrinkLayoutSize(true)
+    , m_topControlsOffsetIsNormalized(true)
 {
     Page::PageClients pageClients;
     pageClients.chromeClient = &m_chromeClientImpl;
@@ -1726,7 +1728,17 @@ void WebViewImpl::setTopControlsContentOffset(float offset)
 
 void WebViewImpl::setTopControlsLayoutHeight(float height)
 {
-    m_topControlsLayoutHeight = height;
+    m_topControlsOffsetIsNormalized = false;
+    setTopControlsHeight(height, true);
+}
+
+void WebViewImpl::setTopControlsHeight(float height, bool topControlsShrinkLayoutSize)
+{
+    if (m_topControlsHeight == height && m_topControlsShrinkLayoutSize == topControlsShrinkLayoutSize)
+        return;
+
+    m_topControlsHeight = height;
+    m_topControlsShrinkLayoutSize = topControlsShrinkLayoutSize;
     didUpdateTopControls();
 }
 
@@ -1740,7 +1752,11 @@ void WebViewImpl::didUpdateTopControls()
     if (!view)
         return;
 
-    float topControlsViewportAdjustment = m_topControlsLayoutHeight - m_topControlsContentOffset;
+    float topControlsViewportAdjustment = 0;
+    if (m_topControlsShrinkLayoutSize)
+        topControlsViewportAdjustment += m_topControlsHeight;
+    topControlsViewportAdjustment -= m_topControlsContentOffset * (m_topControlsOffsetIsNormalized ? m_topControlsHeight : 1);
+
     if (!pinchVirtualViewportEnabled()) {
         // 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