Image filters: optimize crop rect application

src/effects/SkMergeImageFilter.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 "SkMergeImageFilter.h"
 
 #include "SkCanvas.h"
@@ skipping 68 matching lines @@
         }
         const SkIRect inputBounds = SkIRect::MakeXYWH(offsets[i].fX, offsets[i].fY,
                                                       inputs[i]->width(), inputs[i]->height());
         bounds.join(inputBounds);
     }
     if (bounds.isEmpty()) {
         return nullptr;
     }
 
     // Apply the crop rect to the union of the inputs' bounds.
-    this->getCropRect().applyTo(bounds, ctx.ctm(), &bounds);
+    // Note that the crop rect can only reduce the bounds, since this
+    // filter does not affect transparent black.
+    bool embiggen = false;
+    this->getCropRect().applyTo(bounds, ctx.ctm(), embiggen, &bounds);
     if (!bounds.intersect(ctx.clipBounds())) {
         return nullptr;
     }
 
     const int x0 = bounds.left();
     const int y0 = bounds.top();
 
     SkImageInfo info = SkImageInfo::MakeN32(bounds.width(), bounds.height(),
                                             kPremul_SkAlphaType);
 
@@ skipping 69 matching lines @@
     for (int i = 0; i < this->countInputs(); ++i) {
         SkImageFilter* filter = this->getInput(i);
         str->appendf("%d: (", i);
         filter->toString(str);
         str->appendf(")");
     }
 
     str->append(")");
 }
 #endif