add assert that the lock-count on pixelref is balanced

BUG=skia:
TBR=

Review URL: https://codereview.chromium.org/1147153004

gyp/skia_for_android_framework_defines.gypi

@@ -15,6 +15,7 @@
     'skia_for_android_framework_defines': [
       'SK_SUPPORT_LEGACY_PUBLIC_IMAGEINFO_FIELDS',
       'SK_SUPPORT_LEGACY_GETDEVICE',
+      'SK_SUPPORT_LEGACY_UNBALANCED_PIXELREF_LOCKCOUNT',
       # Needed until we fix skbug.com/2440.
       'SK_SUPPORT_LEGACY_CLIPTOLAYERFLAG',
       'SK_IGNORE_LINEONLY_AA_CONVEX_PATH_OPTS',

src/core/SkPixelRef.cpp

@@ -10,6 +10,7 @@
 #include "SkThread.h"
 #include "SkTraceEvent.h"
 
+//#define SK_SUPPORT_LEGACY_UNBALANCED_PIXELREF_LOCKCOUNT
 //#define SK_TRACE_PIXELREF_LIFETIME
 
 #ifdef SK_BUILD_FOR_WIN32
@@ -130,6 +131,10 @@ SkPixelRef::SkPixelRef(const SkImageInfo& info, SkBaseMutex* mutex)
 }
 
 SkPixelRef::~SkPixelRef() {
+#ifndef SK_SUPPORT_LEGACY_UNBALANCED_PIXELREF_LOCKCOUNT
+    SkASSERT(SKPIXELREF_PRELOCKED_LOCKCOUNT == fLockCount || 0 == fLockCount);
+#endif
+
 #ifdef SK_TRACE_PIXELREF_LIFETIME
     SkDebugf("~pixelref %d\n", sk_atomic_dec(&gInstCounter) - 1);
 #endif

tests/CachedDecodingPixelRefTest.cpp

@@ -262,11 +262,13 @@ static void check_pixelref(TestImageGenerator::TestType type,
 
 // new/lock/delete is an odd pattern for a pixelref, but it needs to not assert
 static void test_newlockdelete(skiatest::Reporter* reporter) {
+#ifdef SK_SUPPORT_LEGACY_UNBALANCED_PIXELREF_LOCKCOUNT
     SkBitmap bm;
     SkImageGenerator* ig = new TestImageGenerator(
         TestImageGenerator::kSucceedGetPixels_TestType, reporter);
     SkInstallDiscardablePixelRef(ig, &bm);
     bm.pixelRef()->lockPixels();
+#endif
 }
 
 /**