Don't set shownRatio in main thread top controls on animated state change.

third_party/WebKit/Source/web/tests/TopControlsTest.cpp

Index: third_party/WebKit/Source/web/tests/TopControlsTest.cpp
diff --git a/third_party/WebKit/Source/web/tests/TopControlsTest.cpp b/third_party/WebKit/Source/web/tests/TopControlsTest.cpp
index a179c520e1466633709cfc736c74f20afa421c3e..42af87a8b541ac9aac38d108d18d2ca511fb962d 100644
--- a/third_party/WebKit/Source/web/tests/TopControlsTest.cpp
+++ b/third_party/WebKit/Source/web/tests/TopControlsTest.cpp
@@ -559,6 +559,21 @@ TEST_F(TopControlsTest, MAYBE(StateConstraints))
     EXPECT_FLOAT_EQ(20, webView->topControls().contentOffset());
     webView->updateTopControlsState(WebTopControlsBoth, WebTopControlsBoth, false);
     EXPECT_FLOAT_EQ(20, webView->topControls().contentOffset());
+
+    // An animated state change shouldn't cause a change to the content offset
+    // since it'll be driven from the compositor.
+    webView->updateTopControlsState(WebTopControlsHidden, WebTopControlsHidden, true);
+    EXPECT_FLOAT_EQ(20, webView->topControls().contentOffset());
+
+    webView->updateTopControlsState(WebTopControlsShown, WebTopControlsShown, true);
+    EXPECT_FLOAT_EQ(20, webView->topControls().contentOffset());
+
+    // Setting just the constraint should affect the content offset.
+    webView->updateTopControlsState(WebTopControlsHidden, WebTopControlsBoth, false);
+    EXPECT_FLOAT_EQ(0, webView->topControls().contentOffset());
+
+    webView->updateTopControlsState(WebTopControlsShown, WebTopControlsBoth, false);
+    EXPECT_FLOAT_EQ(50, webView->topControls().contentOffset());
 }
 
 // Ensure that top controls do not affect the layout by showing and hiding