switch GatherPixelRefs to use SkBaseDevice instead of SkBitmapDevice

src/gpu/SkGpuDevice.cpp

Index: src/gpu/SkGpuDevice.cpp
diff --git a/src/gpu/SkGpuDevice.cpp b/src/gpu/SkGpuDevice.cpp
index 429ee9f8e230c519af2f52b5cd593f15537abbc4..747688ed8b6371a48e3af6f6c2d26285ede30888 100644
--- a/src/gpu/SkGpuDevice.cpp
+++ b/src/gpu/SkGpuDevice.cpp
@@ -513,13 +513,6 @@ inline bool skPaint2GrPaintShader(SkGpuDevice* dev,
 }
 
 ///////////////////////////////////////////////////////////////////////////////
-void SkGpuDevice::getGlobalBounds(SkIRect* bounds) const {
-    if (NULL != bounds) {
-        const SkIPoint& origin = this->getOrigin();
-        bounds->setXYWH(origin.x(), origin.y(),
-                        this->width(), this->height());
-    }
-}
 
 SkBitmap::Config SkGpuDevice::config() const {
     if (NULL == fRenderTarget) {