Don't null the reference to Bitmap pixels until we're really ready

A change in the VM triggers a native memory error more aggressively than before,
showing that there's a bug in the logic of recycling bitmaps. Since the pixel
memory is allocated on the Java heap, nulling out the reference to that memory
in the Java level Bitmap object can cause that memory to get collected at any time.
Meanwhile, we may have a reference to that memory at the native level for rendering
purposes, causing an error if/when we access that memory after it has been collected
by the VM.

The fix is to avoid setting the reference to the pixels to null unless we are
not referring to it in native code. This is determined at the time we call
recycle() - we return a boolean to indicate whether the native code is still
using the memory. if not, the Java code can null out the reference and allow the
VM to collect it. Otherwise, it will get collected later when the encompassing
Bitmap object is collected.

Issue #7339156 HTML5 tests crash the app (Vellamo)

Change-Id: I3a0d6b9a6c5dd3b86cc2b0ff7719007e774b5e3c

1 files changed, 9 insertions, 4 deletions

diff --git a/graphics/java/android/graphics/Bitmap.java b/graphics/java/android/graphics/Bitmap.java
index 22ecc61..688fd7a 100644
--- a/graphics/java/android/graphics/Bitmap.java
+++ b/graphics/java/android/graphics/Bitmap.java
@@ -201,9 +201,14 @@ public final class Bitmap implements Parcelable {
      */
     public void recycle() {
         if (!mRecycled) {
-            mBuffer = null;
-            nativeRecycle(mNativeBitmap);
-            mNinePatchChunk = null;
+            if (nativeRecycle(mNativeBitmap)) {
+                // return value indicates whether native pixel object was actually recycled.
+                // false indicates that it is still in use at the native level and these
+                // objects should not be collected now. They will be collected later when the
+                // Bitmap itself is collected.
+                mBuffer = null;
+                mNinePatchChunk = null;
+            }
             mRecycled = true;
         }
     }
@@ -1391,7 +1396,7 @@ public final class Bitmap implements Parcelable {
     private static native Bitmap nativeCopy(int srcBitmap, int nativeConfig,
                                             boolean isMutable);
     private static native void nativeDestructor(int nativeBitmap);
-    private static native void nativeRecycle(int nativeBitmap);
+    private static native boolean nativeRecycle(int nativeBitmap);
 
     private static native boolean nativeCompress(int nativeBitmap, int format,
                                             int quality, OutputStream stream,