Add a PNGEncoder helper function that takes an SkBitmap,

base/gfx/png_encoder.h

Index: base/gfx/png_encoder.h
diff --git a/base/gfx/png_encoder.h b/base/gfx/png_encoder.h
old mode 100644
new mode 100755
index e346bd0ec332f6fd780e69087954b1012a59d50b..7d284bee1b8e64bc11bf90f8824f4c83972cf042
--- a/base/gfx/png_encoder.h
+++ b/base/gfx/png_encoder.h
@@ -9,6 +9,8 @@
 
 #include "base/basictypes.h"
 
+class SkBitmap;
+
 // Interface for encoding PNG data. This is a wrapper around libpng,
 // which has an inconvenient interface for callers. This is currently designed
 // for use in tests only (where we control the files), so the handling isn't as
@@ -51,6 +53,14 @@ class PNGEncoder {
                      bool discard_transparency,
                      std::vector<unsigned char>* output);
 
+  // Call PNGEncoder::Encode on the supplied SkBitmap |input|, which is assumed
+  // to be BGRA, 32 bits per pixel. The params |discard_transparency| and
+  // |output| are passed directly to Encode; refer to Encode for more
+  // information. During the call, an SkAutoLockPixels lock is held on |input|.
+  static bool EncodeBGRASkBitmap(const SkBitmap& input,
+                                 bool discard_transparency,
+                                 std::vector<unsigned char>* output);
+
  private:
   DISALLOW_EVIL_CONSTRUCTORS(PNGEncoder);
 };