Reland of Implement canComputeFastBounds() for image filters.

src/core/SkImageFilter.cpp

 /*
  * Copyright 2012 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 "SkImageFilter.h"
 
 #include "SkBitmap.h"
@@ skipping 266 matching lines @@
         if (input) {
             SkRect bounds;
             input->computeFastBounds(src, &bounds);
             dst->join(bounds);
         } else {
             dst->join(src);
         }
     }
 }
 
+bool SkImageFilter::canComputeFastBounds() const {
+    if (this->affectsTransparentBlack()) {
+        return false;
+    }
+    for (int i = 0; i < fInputCount; i++) {
+        SkImageFilter* input = this->getInput(i);
+        if (input && !input->canComputeFastBounds()) {
+            return false;
+        }
+    }
+    return true;
+}
+
+bool SkImageFilter::affectsTransparentBlack() const {
+    return false;
+}
+
 bool SkImageFilter::onFilterImage(Proxy*, const SkBitmap&, const Context&,
                                   SkBitmap*, SkIPoint*) const {
     return false;
 }
 
 bool SkImageFilter::canFilterImageGPU() const {
     return this->asFragmentProcessor(NULL, NULL, NULL, SkMatrix::I(), SkIRect());
 }
 
 bool SkImageFilter::filterImageGPU(Proxy* proxy, const SkBitmap& src, const Context& ctx,
@@ skipping 281 matching lines @@
     }
     return dev;
 }
 
 bool SkImageFilter::Proxy::filterImage(const SkImageFilter* filter, const SkBitmap& src,
                                        const SkImageFilter::Context& ctx,
                                        SkBitmap* result, SkIPoint* offset) {
     return fDevice->filterImage(filter, src, ctx, result, offset);
 }