add SkPixmap and external locking to bitmaps

include/core/SkBitmap.h

Index: include/core/SkBitmap.h
diff --git a/include/core/SkBitmap.h b/include/core/SkBitmap.h
index dbaca621af93192c184188910f5f22077062927e..7baa33e5c3da9456e0b4a4fdf30c5f98e4851c73 100644
--- a/include/core/SkBitmap.h
+++ b/include/core/SkBitmap.h
@@ -11,6 +11,7 @@
 #include "SkColor.h"
 #include "SkColorTable.h"
 #include "SkImageInfo.h"
+#include "SkPixmap.h"
 #include "SkPoint.h"
 #include "SkRefCnt.h"
 
@@ -428,6 +429,34 @@ public:
      */
     bool lockPixelsAreWritable() const;
 
+    class LockResult {

[scroggo, 2015/05/19 20:11:41]

inherit from SkNoncopyable?

[reed1, 2015/05/21 20:59:34]

Done.

+    public:
+        LockResult() : fUnlockProc(NULL), fUnlockContext(NULL) {
+            SkDEBUGCODE(fIsLocked = false;)
+        }
+
+        const SkPixmap& pixmap() const { return fPixmap; }
+
+        SkDEBUGCODE(bool isLocked() const { return fIsLocked; })
+        void unlock();

[scroggo, 2015/05/19 20:11:42]

Should this get called by a destructor, if it wasn't called before?

[reed1, 2015/05/21 20:59:34]

Done.

+
+    private:
+        LockResult(const SkPixmap& pm, void (*unlock)(void*), void* ctx)
+            : fUnlockProc(unlock), fUnlockContext(ctx), fPixmap(pm)
+        {
+            SkDEBUGCODE(fIsLocked = true;)
+        }
+
+        void        (*fUnlockProc)(void*);
+        void*       fUnlockContext;
+        SkPixmap    fPixmap;
+        SkDEBUGCODE(bool fIsLocked;)
+
+        friend class SkBitmap;
+    };
+
+    bool requestLock(LockResult* result) const;
+
     /** Call this to be sure that the bitmap is valid enough to be drawn (i.e.
         it has non-null pixels, and if required by its colortype, it has a
         non-null colortable. Returns true if all of the above are met.
@@ -783,6 +812,14 @@ private:
 //TODO(mtklein): uncomment when 71713004 lands and Chromium's fixed.
 //#define SkAutoLockPixels(...) SK_REQUIRE_LOCAL_VAR(SkAutoLockPixels)
 
+class SkAutoBitmapLockResult : public SkBitmap::LockResult {
+public:
+    SkAutoBitmapLockResult() {}
+    ~SkAutoBitmapLockResult() {
+        this->unlock();
+    }
+};
+
 ///////////////////////////////////////////////////////////////////////////////
 
 inline uint32_t* SkBitmap::getAddr32(int x, int y) const {