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

Reason for revert: Failing assert on Android

R=scroggo@google.com, halcanary@google.com, reed@google.com, rmistry@google.com
TBR=halcanary@google.com, reed@google.com, scroggo@google.com
NOTREECHECKS=true
NOTRY=true

Author: robertphillips@google.com

Review URL: https://codereview.chromium.org/93673005

git-svn-id: http://skia.googlecode.com/svn/trunk@12646 2bbb7eff-a529-9590-31e7-b0007b416f81

include/core/SkPixelRef.h

@@ -244,15 +244,10 @@ protected:
         acquire a mutex for thread safety, so this method need not do that.
     */
     virtual void* onLockPixels(SkColorTable**) = 0;
- 
-    /**
-     *  Called when the lock count goes from 1 to 0. The caller will have
-     *  already acquire a mutex for thread safety, so this method need not do
-     *  that.
-     *
-     *  If the previous call to onLockPixels failed (i.e. returned NULL), then
-     *  the onUnlockPixels will NOT be called.
-     */
+    /** Called when the lock count goes from 1 to 0. The caller will have
+        already acquire a mutex for thread safety, so this method need not do
+        that.
+    */
     virtual void onUnlockPixels() = 0;
 
     /** Default impl returns true */

src/core/SkPixelRef.cpp

@@ -182,10 +182,6 @@ void SkPixelRef::lockPixels() {
 
         if (1 == ++fLockCount) {
             fPixels = this->onLockPixels(&fColorTable);
-            // If onLockPixels failed, it will return NULL
-            if (NULL == fPixels) {
-                fColorTable = NULL;
-            }
         }
     }
 }
@@ -198,14 +194,9 @@ void SkPixelRef::unlockPixels() {
 
         SkASSERT(fLockCount > 0);
         if (0 == --fLockCount) {
-            // don't call onUnlockPixels unless onLockPixels succeeded
-            if (fPixels) {
-                this->onUnlockPixels();
-                fPixels = NULL;
-                fColorTable = NULL;
-            } else {
-                SkASSERT(NULL == fColorTable);
-            }
+            this->onUnlockPixels();
+            fPixels = NULL;
+            fColorTable = NULL;
         }
     }
 }

src/core/SkScaledImageCache.cpp

@@ -209,6 +209,7 @@ private:
     SkDiscardableMemory* fDM;
     size_t               fRB;
     bool                 fFirstTime;
+    bool                 fIsLocked;
 
     typedef SkPixelRef INHERITED;
 };
@@ -224,6 +225,7 @@ SkOneShotDiscardablePixelRef::SkOneShotDiscardablePixelRef(const SkImageInfo& in
 
     SkASSERT(dm->data());
     fFirstTime = true;
+    fIsLocked = false;
 }
 
 SkOneShotDiscardablePixelRef::~SkOneShotDiscardablePixelRef() {
@@ -233,16 +235,21 @@ SkOneShotDiscardablePixelRef::~SkOneShotDiscardablePixelRef() {
 void* SkOneShotDiscardablePixelRef::onLockPixels(SkColorTable** ctable) {
     if (fFirstTime) {
         // we're already locked
-        SkASSERT(fDM->data());
         fFirstTime = false;
         return fDM->data();
     }
-    return fDM->lock() ? fDM->data() : NULL;
+
+    SkASSERT(!fIsLocked);
+    fIsLocked = fDM->lock();
+    return fIsLocked ? fDM->data() : NULL;
 }
 
 void SkOneShotDiscardablePixelRef::onUnlockPixels() {
     SkASSERT(!fFirstTime);
-    fDM->unlock();
+    if (fIsLocked) {
+        fIsLocked = false;
+        fDM->unlock();
+    }
 }
 
 size_t SkOneShotDiscardablePixelRef::getAllocatedSizeInBytes() const {

src/images/SkImageRef_ashmem.cpp

@@ -1,10 +1,10 @@
+
 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
-
 #include "SkImageRef_ashmem.h"
 #include "SkImageDecoder.h"
 #include "SkFlattenableBuffers.h"

src/lazy/SkCachingPixelRef.cpp

@@ -90,7 +90,9 @@ void* SkCachingPixelRef::onLockPixels(SkColorTable** colorTable) {
 }
 
 void SkCachingPixelRef::onUnlockPixels() {
-    SkASSERT(fScaledCacheId != NULL);
-    SkScaledImageCache::Unlock( static_cast<SkScaledImageCache::ID*>(fScaledCacheId));
-    fScaledCacheId = NULL;
+    if (fScaledCacheId != NULL) {
+        SkScaledImageCache::Unlock(
+            static_cast<SkScaledImageCache::ID*>(fScaledCacheId));
+        fScaledCacheId = NULL;
+    }
 }

src/lazy/SkDiscardablePixelRef.cpp

@@ -58,7 +58,9 @@ void* SkDiscardablePixelRef::onLockPixels(SkColorTable**) {
     return pixels;
 }
 void SkDiscardablePixelRef::onUnlockPixels() {
-    fDiscardableMemory->unlock();
+    if (fDiscardableMemory != NULL) {
+        fDiscardableMemory->unlock();
+    }
 }
 
 bool SkInstallDiscardablePixelRef(SkImageGenerator* generator,