Sk_API for SkImageGenerator and SkInstallDiscardablePixelRef

Added SK_API to SkImageGenerator (already in include/).

Moved SkDiscardablePixelRef::Install to SkInstallDiscardablePixelRef,
added SK_API to that function, and moved declaration to
SkImageGenerator.h

This keeps the SkDiscardablePixelRef internal to Skia, but exposes a
method to install it into a bitmap.

Modifed tests that rely on this functio to use new version.

BUG=
R=mtklein@google.com, reed@google.com

Review URL: https://codereview.chromium.org/111713002

git-svn-id: http://skia.googlecode.com/svn/trunk@12612 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/images/SkDecodingImageGenerator.cpp b/src/images/SkDecodingImageGenerator.cpp
index 2121049..a833c63 100644
--- a/src/images/SkDecodingImageGenerator.cpp
+++ b/src/images/SkDecodingImageGenerator.cpp
@@ -7,8 +7,8 @@
 
 #include "SkDecodingImageGenerator.h"
 #include "SkData.h"
-#include "SkDiscardablePixelRef.h"
 #include "SkImageDecoder.h"
+#include "SkImageGenerator.h"
 #include "SkImagePriv.h"
 #include "SkStream.h"
 
@@ -191,7 +191,7 @@
     SkASSERT(data != NULL);
     SkASSERT(dst != NULL);
     SkImageGenerator* gen(SkNEW_ARGS(SkDecodingImageGenerator, (data)));
-    return SkDiscardablePixelRef::Install(gen, dst, factory);
+    return SkInstallDiscardablePixelRef(gen, dst, factory);
 }
 
 bool SkDecodingImageGenerator::Install(SkStreamRewindable* stream,
@@ -204,5 +204,5 @@
         return false;
     }
     SkImageGenerator* gen(SkNEW_ARGS(SkDecodingImageGenerator, (stream)));
-    return SkDiscardablePixelRef::Install(gen, dst, factory);
+    return SkInstallDiscardablePixelRef(gen, dst, factory);
 }