Revert "Revert of https://codereview.chromium.org/112783004/"

This reverts commit 3293fe57a7507541e9040eab880dcd82c43881f4.

Conflicts:
	src/core/SkScaledImageCache.cpp

BUG=

Review URL: https://codereview.chromium.org/108613005

git-svn-id: http://skia.googlecode.com/svn/trunk@12663 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/core/SkScaledImageCache.cpp b/src/core/SkScaledImageCache.cpp
index 7c8b664..2529b5f 100644
--- a/src/core/SkScaledImageCache.cpp
+++ b/src/core/SkScaledImageCache.cpp
@@ -209,7 +209,6 @@
     SkDiscardableMemory* fDM;
     size_t               fRB;
     bool                 fFirstTime;
-    bool                 fIsLocked;
 
     typedef SkPixelRef INHERITED;
 };
@@ -225,7 +224,6 @@
 
     SkASSERT(dm->data());
     fFirstTime = true;
-    fIsLocked = false;
 }
 
 SkOneShotDiscardablePixelRef::~SkOneShotDiscardablePixelRef() {
@@ -235,6 +233,7 @@
 void* SkOneShotDiscardablePixelRef::onLockPixels(SkColorTable** ctable) {
     if (fFirstTime) {
         // we're already locked
+        SkASSERT(fDM->data());
         fFirstTime = false;
         return fDM->data();
     }
@@ -255,10 +254,7 @@
 
 void SkOneShotDiscardablePixelRef::onUnlockPixels() {
     SkASSERT(!fFirstTime);
-    if (fIsLocked) {
-        fIsLocked = false;
-        fDM->unlock();
-    }
+    fDM->unlock();
 }
 
 size_t SkOneShotDiscardablePixelRef::getAllocatedSizeInBytes() const {