Remove transient and unnecessary update density message.

On a page load, the (viewport) metadata settings for the main frame are
reset. Reloading a page with viewport meta tag specifying target density
dpi will result in 2 back to back update zoom density messages to be
sent from WebViewCore to UI thread.

In setupViewport(), remove update density messages in flight. If the new
density is indeed different from WebView's default scale, queue another
message.

Bug: 6509512
Change-Id: I195e40277bf1bcccb0e61d84ed84db1e34556243

Author: mghiware

core/java/android/webkit/WebViewCore.java

@@ -2550,6 +2550,11 @@ private void setupViewport(boolean updateViewState) {
             adjust = (float) mContext.getResources().getDisplayMetrics().densityDpi
                     / mViewportDensityDpi;
         }
+        // Remove any update density messages in flight.
+        // If the density is indeed different from WebView's default scale,
+        // a new message will be queued.
+        mWebViewClassic.mPrivateHandler.removeMessages(
+                WebViewClassic.UPDATE_ZOOM_DENSITY);
         if (adjust != mWebViewClassic.getDefaultZoomScale()) {
             Message.obtain(mWebViewClassic.mPrivateHandler,
                     WebViewClassic.UPDATE_ZOOM_DENSITY, adjust).sendToTarget();