Update tab switcher state in ToolbarPhone after animation completes

Previously onTabSwitcherTransitionFinished was only called when
exiting the tab switcher. This change implements
onOverviewModeFinishedShowing to call this method.

BUG=710750

Change-Id: I1a34551a6cd93a54a9461441c25ce022144efa9e
Reviewed-on: https://chromium-review.googlesource.com/929991Reviewed-by: David Trainor <dtrainor@chromium.org>
Reviewed-by: Ted Choc <tedchoc@chromium.org>
Commit-Queue: Matthew Jones <mdjones@chromium.org>
Cr-Commit-Position: refs/heads/master@{#539205}

chrome/android/java/src/org/chromium/chrome/browser/toolbar/ToolbarManager.java

@@ -593,6 +593,11 @@ public class ToolbarManager implements ToolbarTabController, UrlFocusChangeListe
             public void onOverviewModeFinishedHiding() {
                 mToolbar.onTabSwitcherTransitionFinished();
             }
+
+            @Override
+            public void onOverviewModeFinishedShowing() {
+                mToolbar.onTabSwitcherTransitionFinished();
+            }
         };
 
         mSceneChangeObserver = new SceneChangeObserver() {