Load assets in place instead of deferring until draw.

Before this change, all framework assets would be decoded at drawing time
outside of zygote. This was forcing all apps to re-decode the assets and
zygote to keep an in-memory copy of each asset. This behavior is now
opt-in by setting the inPurgeable flag on BitmapFactory.Options.

Change-Id: Ic703f57adb26b2a701ecff0a653d35a93e26d47c

core/jni/android/graphics/BitmapFactory.cpp

@@ -218,6 +218,7 @@ static SkPixelRef* installPixelRef(SkBitmap* bitmap, SkStream* stream,
     }
     pr->setDitherImage(ditherImage);
     bitmap->setPixelRef(pr)->unref();
+    pr->isOpaque(bitmap);
     return pr;
 }
 
@@ -464,10 +465,7 @@ static jobject nativeDecodeAsset(JNIEnv* env, jobject clazz,
                                  jobject options) { // BitmapFactory$Options
     SkStream* stream;
     Asset* asset = reinterpret_cast<Asset*>(native_asset);
-    // assets can always be rebuilt, so force this
-    bool forcePurgeable = true;
-
-    if (forcePurgeable || optionsPurgeable(env, options)) {
+    if (optionsPurgeable(env, options)) {
         // if we could "ref/reopen" the asset, we may not need to copy it here
         // and we could assume optionsShareable, since assets are always RO
         stream = copyAssetToStream(asset);