Use Identity matrix for SkTransparentShader.

src/core/SkBlitter.cpp

 /*
  * Copyright 2006 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 "SkBlitter.h"
 #include "SkAntiRun.h"
 #include "SkColor.h"
@@ skipping 978 matching lines @@
                 static_cast<Sk3DShader::Sk3DShaderContext*>(shaderContext));
     }
     return blitter;
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 
 class SkTransparentShaderContext : public SkShader::Context {
 public:
     SkTransparentShaderContext(const SkShader& shader, const SkShader::ContextRec& rec)
-        : INHERITED(shader, rec) {}
+        // Override rec with the identity matrix, so it is guaranteed to be invertible.
+        : INHERITED(shader, SkShader::ContextRec(*rec.fDevice, *rec.fPaint, SkMatrix::I())) {}
 
     virtual void shadeSpan(int x, int y, SkPMColor colors[], int count) SK_OVERRIDE {
         sk_bzero(colors, count * sizeof(SkPMColor));
     }
 
 private:
     typedef SkShader::Context INHERITED;
 };
 
 SkShaderBlitter::SkShaderBlitter(const SkBitmap& device, const SkPaint& paint,
@@ skipping 21 matching lines @@
     fShaderContext->~Context();
     SkShader::Context* ctx = fShader->createContext(rec, (void*)fShaderContext);
     if (NULL == ctx) {
         // Need a valid context in fShaderContext's storage, so we can later (or our caller) call
         // the in-place destructor.
         SkNEW_PLACEMENT_ARGS(fShaderContext, SkTransparentShaderContext, (*fShader, rec));
         return false;
     }
     return true;
 }