aw: Update canvas translate after draw

This is a follow up to r370808. After r370808, the result of
ComputeScroll will be reflected on UI thread at the end of
draw, so is not reflected in the transform in the canvas
passed to onDraw.

Webview rendering code is designed to handle this case.
However anything drawn after webview will be using the
incorrect translate. This includes webview's children, and
the default scroll bar.

The fix for this is to simply update the translate of the
canvas with the new scroll offset.

BUG=545633

Review URL: https://codereview.chromium.org/1621793002

Cr-Commit-Position: refs/heads/master@{#371030}

1 files changed, 10 insertions, 6 deletions

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 9140cd4..26980b9 100644
--- a/android_webview/java/src/org/chromium/android_webview/AwContents.java
+++ b/android_webview/java/src/org/chromium/android_webview/AwContents.java
@@ -2903,16 +2903,20 @@ public class AwContents implements SmartClipProvider,
             }
 
             mScrollOffsetManager.syncScrollOffsetFromOnDraw();
+            int scrollX = mContainerView.getScrollX();
+            int scrollY = mContainerView.getScrollY();
             Rect globalVisibleRect = getGlobalVisibleRect();
-            boolean did_draw = nativeOnDraw(
-                    mNativeAwContents, canvas, canvas.isHardwareAccelerated(),
-                    mContainerView.getScrollX(), mContainerView.getScrollY(),
-                    globalVisibleRect.left, globalVisibleRect.top,
-                    globalVisibleRect.right, globalVisibleRect.bottom);
+            boolean did_draw = nativeOnDraw(mNativeAwContents, canvas,
+                    canvas.isHardwareAccelerated(), scrollX, scrollY, globalVisibleRect.left,
+                    globalVisibleRect.top, globalVisibleRect.right, globalVisibleRect.bottom);
             if (did_draw && canvas.isHardwareAccelerated() && !FORCE_AUXILIARY_BITMAP_RENDERING) {
                 did_draw = mNativeGLDelegate.requestDrawGL(canvas, false, mContainerView);
             }
-            if (!did_draw) {
+            if (did_draw) {
+                int scrollXDiff = mContainerView.getScrollX() - scrollX;
+                int scrollYDiff = mContainerView.getScrollY() - scrollY;
+                canvas.translate(-scrollXDiff, -scrollYDiff);
+            } else {
                 TraceEvent.instant("NativeDrawFailed");
                 canvas.drawColor(getEffectiveBackgroundColor());
             }