Close AndroidOverlay client to prevent leaked mojo routers.

Previously, DialogOverlayImpl did not close the overlay client when
cleaning up.  This caused the mojo router in |mClient| to be closed
only when the client was GC'd, and issued warnings in logcat.

Now, DialogOverlayImpl closes |mClient| properly.

AndroidOverlayProviderImpl also closes the client if it fails before
providing the client to a DialogOverlayImpl.

Bug: 822798
Change-Id: I57657b4e1bc77e07e79a1182c5467e243d947002
Reviewed-on: https://chromium-review.googlesource.com/966868Reviewed-by: Bo <boliu@chromium.org>
Reviewed-by: Luke Halliwell <halliwell@chromium.org>
Commit-Queue: Frank Liberato <liberato@chromium.org>
Cr-Commit-Position: refs/heads/master@{#543770}

content/public/android/java/src/org/chromium/content/browser/androidoverlay/AndroidOverlayProviderImpl.java

@@ -66,6 +66,7 @@ public class AndroidOverlayProviderImpl implements AndroidOverlayProvider {
         // Limit the number of concurrent surfaces.
         if (mNumOverlays >= MAX_OVERLAYS) {
             client.onDestroyed();
+            client.close();
             return;
         }
 

content/public/android/java/src/org/chromium/content/browser/androidoverlay/DialogOverlayImpl.java

@@ -309,6 +309,8 @@ public class DialogOverlayImpl implements AndroidOverlay, DialogOverlayCore.Host
         mDialogCore = null;
 
         // If we wanted to send any message to |mClient|, we should have done so already.
+        // We close |mClient| first to prevent leaking the mojo router object.
+        if (mClient != null) mClient.close();
         mClient = null;
     }