Simplify SkGpuDevice construction

R=robertphillips@google.com, reed@google.com

Author: bsalomon@google.com

Review URL: https://codereview.chromium.org/506413004
diff --git a/include/gpu/SkGpuDevice.h b/include/gpu/SkGpuDevice.h
index 96f3d84..838abc1 100644
--- a/include/gpu/SkGpuDevice.h
+++ b/include/gpu/SkGpuDevice.h
@@ -110,12 +110,6 @@
 
     virtual const SkBitmap& onAccessBitmap() SK_OVERRIDE;
 
-    /**
-     * Make's this device's rendertarget current in the underlying 3D API.
-     * Also implicitly flushes.
-     */
-    virtual void makeRenderTargetCurrent();
-
     virtual bool canHandleImageFilter(const SkImageFilter*) SK_OVERRIDE;
     virtual bool filterImage(const SkImageFilter*, const SkBitmap&,
                              const SkImageFilter::Context&,
@@ -160,12 +154,7 @@
     // remove when our clients don't rely on accessBitmap()
     SkBitmap fLegacyBitmap;
 
-    SkGpuDevice(GrContext*, GrRenderTarget*, unsigned flags = 0);
-
-    SkGpuDevice(GrContext*, GrTexture*, unsigned flags = 0);
-
-    // called from rt and tex cons
-    void initFromRenderTarget(GrContext*, GrRenderTarget*, unsigned flags);
+    SkGpuDevice(GrSurface*, unsigned flags = 0);
 
     virtual SkBaseDevice* onCreateDevice(const SkImageInfo&, Usage) SK_OVERRIDE;