Implement clearView to match classic

android_webview/java/src/org/chromium/android_webview/AwContents.java

Index: android_webview/java/src/org/chromium/android_webview/AwContents.java
diff --git a/android_webview/java/src/org/chromium/android_webview/AwContents.java b/android_webview/java/src/org/chromium/android_webview/AwContents.java
index 1e7f88d16b5d9c8dba1c7717085b88bfbb4c9ad1..fe1d0d35b161f0e6b33bb1f0178a6700629a359f 100644
--- a/android_webview/java/src/org/chromium/android_webview/AwContents.java
+++ b/android_webview/java/src/org/chromium/android_webview/AwContents.java
@@ -180,6 +180,9 @@ public class AwContents {
     private boolean mContainerViewFocused;
     private boolean mWindowFocused;
 
+    private boolean mClearViewActive;
+    private boolean mPictureListenerEnabled;
+
     private AwAutofillManagerDelegate mAwAutofillManagerDelegate;
 
     private static final class DestroyRunnable implements Runnable {
@@ -694,12 +697,14 @@ public class AwContents {
         }
 
         mScrollOffsetManager.syncScrollOffsetFromOnDraw();
-
         canvas.getClipBounds(mClipBoundsTemporary);
-        if (!nativeOnDraw(mNativeAwContents, canvas, canvas.isHardwareAccelerated(),
-                    mContainerView.getScrollX(), mContainerView.getScrollY(),
-                    mClipBoundsTemporary.left, mClipBoundsTemporary.top,
-                    mClipBoundsTemporary.right, mClipBoundsTemporary.bottom)) {
+
+        if (mClearViewActive) {
+            canvas.drawColor(getEffectiveBackgroundColor());
+        } else if (!nativeOnDraw(mNativeAwContents, canvas, canvas.isHardwareAccelerated(),
+                mContainerView.getScrollX(), mContainerView.getScrollY(),
+                mClipBoundsTemporary.left, mClipBoundsTemporary.top,
+                mClipBoundsTemporary.right, mClipBoundsTemporary.bottom)) {
             Log.w(TAG, "nativeOnDraw failed; clearing to background color.");
             canvas.drawColor(getEffectiveBackgroundColor());
         }
@@ -729,6 +734,11 @@ public class AwContents {
                     mScrollOffsetManager.computeVerticalScrollRange()));
     }
 
+    public void clearView() {
+        mClearViewActive = true;
+        nativeEnableOnNewPicture(mNativeAwContents, true);

[joth, 2013/08/16 21:41:04]

invalidate();

[Kristian Monsen, 2013/08/16 22:57:10]

Done.

+    }
+
     /**
      * Enable the onNewPicture callback.
      * @param enabled Flag to enable the callback.
@@ -745,6 +755,10 @@ public class AwContents {
                 }
             };
         }
+        mPictureListenerEnabled = enabled;
+        if (mClearViewActive) {
+            enabled = true;
+        }
         nativeEnableOnNewPicture(mNativeAwContents, enabled);

[joth, 2013/08/16 21:41:04]

suggest collecting all three nativeEnableOnNewPicture() calls into a single
make-it-so method:

syncOnNewPictureStateToNative() {
  nativeEnableOnNewPicture(mNativeAwContents, mPictureListenerEnabled ||
mClearViewActive);

[Kristian Monsen, 2013/08/16 22:57:10]

Done.

     }
 
@@ -1685,6 +1699,10 @@ public class AwContents {
 
     @CalledByNative
     public void onNewPicture() {
+        // Clear up any results from a previous clearView call
+        mClearViewActive = false;

[joth, 2013/08/16 21:41:04]

if (mClearViewActive) {
  invalidate();
  mClearViewActive = false;
  syncOnNewPictureStateToNative();
}

could even change the last line to:
  if (!mPictureListenerEnabled) {
    syncOnNewPictureStateToNative();
    return;
  }

[Kristian Monsen, 2013/08/16 22:57:10]

Done.

+        nativeEnableOnNewPicture(mNativeAwContents, mPictureListenerEnabled);
+
         // Don't call capturePicture() here but instead defer it until the posted task runs within
         // the callback helper, to avoid doubling back into the renderer compositor in the middle
         // of the notification it is sending up to here.