Clear the WebView picture when a new load starts.

Clear the old picture set when we have confirmed a new
page load.

Bug: 5701197
Change-Id: Id96fb7d8e75a0b54a448d35239a69ba1774cffae

core/java/android/webkit/BrowserFrame.java

@@ -410,6 +410,7 @@ class BrowserFrame extends Handler {
                 mCommitted = false;
                 // remove pending draw to block update until mFirstLayoutDone is
                 // set to true in didFirstLayout()
+                mWebViewCore.clearContent();
                 mWebViewCore.removeMessages(WebViewCore.EventHub.WEBKIT_DRAW);
             }
         }

core/java/android/webkit/WebViewCore.java

@@ -497,6 +497,13 @@ public final class WebViewCore {
         message.sendToTarget();
     }
 
+    /**
+     * Clear the picture set. To be called only on the WebCore thread.
+     */
+    /* package */ void clearContent() {
+        nativeClearContent();
+    }
+
     //-------------------------------------------------------------------------
     // JNI methods
     //-------------------------------------------------------------------------
@@ -1560,7 +1567,7 @@ public final class WebViewCore {
                             // Clear the view so that onDraw() will draw nothing
                             // but white background
                             // (See public method WebView.clearView)
-                            nativeClearContent();
+                            clearContent();
                             break;
 
                         case MESSAGE_RELAY: