delete (unused) TransparentShader

BUG=skia:
TBR=

Review URL: https://codereview.chromium.org/1153193014
diff --git a/include/core/SkShader.h b/include/core/SkShader.h
index 4c4dba3..3739c9c 100644
--- a/include/core/SkShader.h
+++ b/include/core/SkShader.h
@@ -5,7 +5,6 @@
  * found in the LICENSE file.
  */
 
-
 #ifndef SkShader_DEFINED
 #define SkShader_DEFINED
 
@@ -114,14 +113,11 @@
      *  ContextRec acts as a parameter bundle for creating Contexts.
      */
     struct ContextRec {
-        ContextRec() : fDevice(NULL), fPaint(NULL), fMatrix(NULL), fLocalMatrix(NULL) {}
-        ContextRec(const SkBitmap& device, const SkPaint& paint, const SkMatrix& matrix)
-            : fDevice(&device)
-            , fPaint(&paint)
+        ContextRec(const SkPaint& paint, const SkMatrix& matrix, const SkMatrix* localM)
+            : fPaint(&paint)
             , fMatrix(&matrix)
-            , fLocalMatrix(NULL) {}
+            , fLocalMatrix(localM) {}
 
-        const SkBitmap* fDevice;        // the bitmap we are drawing into
         const SkPaint*  fPaint;         // the current paint associated with the draw
         const SkMatrix* fMatrix;        // the current matrix in the canvas
         const SkMatrix* fLocalMatrix;   // optional local matrix