Avoid sending empty bitmaps through proxy canvas

src/core/SkCanvas.cpp

 /*
  * Copyright 2008 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkCanvas.h"
 #include "SkCanvasPriv.h"
 #include "SkBitmapDevice.h"
@@ skipping 1651 matching lines @@
 void SkCanvas::drawImage(const SkImage* image, SkScalar dx, SkScalar dy, const SkPaint* paint) {
     this->onDrawImage(image, dx, dy, paint);
 }
 
 void SkCanvas::drawImageRect(const SkImage* image, const SkRect* src, const SkRect& dst,
                              const SkPaint* paint) {
     this->onDrawImageRect(image, src, dst, paint);
 }
 
 void SkCanvas::drawBitmap(const SkBitmap& bitmap, SkScalar dx, SkScalar dy, const SkPaint* paint) {
+    if (bitmap.empty()) {
+        return;
+    }
     this->onDrawBitmap(bitmap, dx, dy, paint);
 }
 
 void SkCanvas::drawBitmapRectToRect(const SkBitmap& bitmap, const SkRect* src, const SkRect& dst,
                                     const SkPaint* paint, DrawBitmapRectFlags flags) {
+    if (bitmap.empty()) {
+        return;
+    }
     this->onDrawBitmapRect(bitmap, src, dst, paint, flags);
 }
 
 void SkCanvas::drawBitmapNine(const SkBitmap& bitmap, const SkIRect& center, const SkRect& dst,
                               const SkPaint* paint) {
+    if (bitmap.empty()) {
+        return;
+    }
     this->onDrawBitmapNine(bitmap, center, dst, paint);
 }
 
 void SkCanvas::drawSprite(const SkBitmap& bitmap, int left, int top, const SkPaint* paint) {
+    if (bitmap.empty()) {
+        return;
+    }
     this->onDrawSprite(bitmap, left, top, paint);
 }
 
 //////////////////////////////////////////////////////////////////////////////
 //  These are the virtual drawing methods
 //////////////////////////////////////////////////////////////////////////////
 
 void SkCanvas::onDiscard() {
     if (fSurfaceBase) {
         fSurfaceBase->aboutToDraw(SkSurface::kDiscard_ContentChangeMode);
@@ skipping 851 matching lines @@
     }
 
     if (matrix) {
         canvas->concat(*matrix);
     }
 }
 
 SkAutoCanvasMatrixPaint::~SkAutoCanvasMatrixPaint() {
     fCanvas->restoreToCount(fSaveCount);
 }