add new copyTo version to SkBitmap, which takes SkColorType

BUG=skia:
R=scroggo@google.com, halcanary@google.com, bsalomon@google.com

Author: reed@google.com

Review URL: https://codereview.chromium.org/171723007

git-svn-id: http://skia.googlecode.com/svn/trunk@13553 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/samplecode/SampleApp.cpp b/samplecode/SampleApp.cpp
index 80ffaaa..c8fbf3d 100644
--- a/samplecode/SampleApp.cpp
+++ b/samplecode/SampleApp.cpp
@@ -1449,7 +1449,7 @@
 
         SkBaseDevice* device = orig->getDevice();
         SkBitmap bmp;
-        if (device->accessBitmap(false).copyTo(&bmp, SkBitmap::kARGB_8888_Config)) {
+        if (device->accessBitmap(false).copyTo(&bmp, kPMColor_SkColorType)) {
             static int gSampleGrabCounter;
             SkString name;
             name.printf("sample_grab_%d.png", gSampleGrabCounter++);