Android: Release resources when tab is invisible in strip layout

The bitmap resources held by LayerTitleCache for tabs are never cleared
by tab strip model. Release resources held for a tab if the tab is
marked invisible in tab strip layout.

BUG=701976

Change-Id: I3539d5aa546d5f002cb2b1a670de5dea52336722
Reviewed-on: https://chromium-review.googlesource.com/977324Reviewed-by: Matthew Jones <mdjones@chromium.org>
Commit-Queue: Siddhartha S <ssid@chromium.org>
Cr-Commit-Position: refs/heads/master@{#545569}

chrome/android/java/src/org/chromium/chrome/browser/compositor/overlays/strip/StripLayoutTab.java

@@ -266,6 +266,9 @@ public class StripLayoutTab implements VirtualView {
      */
     public void setVisible(boolean visible) {
         mVisible = visible;
+        if (!visible) {
+            mUpdateHost.releaseResourcesForTab(mId);
+        }
         for (Observer observer : mObservers) {
             observer.onVisibilityChanged(mVisible);
         }