implement isABitmap for imageshader, return localmatrix for bitmap's impl

src/pdf/SkPDFShader.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #include "SkPDFShader.h"
 
@@ skipping 1271 matching lines @@
           fBBox(bbox) {
     fInfo.fColorCount = 0;
     fInfo.fColors = nullptr;
     fInfo.fColorOffsets = nullptr;
     fShaderTransform = shader->getLocalMatrix();
     fImageTileModes[0] = fImageTileModes[1] = SkShader::kClamp_TileMode;
 
     fType = shader->asAGradient(&fInfo);
 
     if (fType == SkShader::kNone_GradientType) {
-        SkMatrix matrix;
-        if (shader->isABitmap(&fImage, &matrix, fImageTileModes)) {
-            SkASSERT(matrix.isIdentity());
-        } else {
+        if (!shader->isABitmap(&fImage, nullptr, fImageTileModes)) {
             // Generic fallback for unsupported shaders:
             //  * allocate a bbox-sized bitmap
             //  * shade the whole area
             //  * use the result as a bitmap shader
 
             // bbox is in device space. While that's exactly what we want for sizing our bitmap,
             // we need to map it into shader space for adjustments (to match
             // SkPDFImageShader::Create's behavior).
             SkRect shaderRect = SkRect::Make(bbox);
             if (!inverse_transform_bbox(canvasTransform, &shaderRect)) {
@@ skipping 105 matching lines @@
     return false;
 }
 
 void SkPDFShader::State::AllocateGradientInfoStorage() {
     fColorData.set(sk_malloc_throw(
                fInfo.fColorCount * (sizeof(SkColor) + sizeof(SkScalar))));
     fInfo.fColors = reinterpret_cast<SkColor*>(fColorData.get());
     fInfo.fColorOffsets =
             reinterpret_cast<SkScalar*>(fInfo.fColors + fInfo.fColorCount);
 }