Prevent crash in WebView when disabling the hw renderer

Bug #6596807

A crash would occur in the following situation:
- WebView registers a functor with the hardware renderer
- The hardware renderer gets disabled
- WebView attemps to unregister its functor

Unregistering the functor fails because the hardware renderer is now disabled.
When the renderer becomes enabled again, the functor is invoked, which leads
to a native crash.

This change simply allows functors to always be unregistered, even when the
renderer is disabled. A disabled renderer only means that it will not be used
for rendering; as such, unregistering a functor is a valid operation and
should be allowed.

Change-Id: I0ff897a0cca7e048c609033215cd0f7f5c940bcc

Author: Romain Guy

core/java/android/view/ViewRootImpl.java

@@ -671,14 +671,15 @@ void destroyHardwareLayers() {
     }
 
     public boolean attachFunctor(int functor) {
+        //noinspection SimplifiableIfStatement
         if (mAttachInfo.mHardwareRenderer != null && mAttachInfo.mHardwareRenderer.isEnabled()) {
             return mAttachInfo.mHardwareRenderer.attachFunctor(mAttachInfo, functor);
         }
         return false;
     }
 
     public void detachFunctor(int functor) {
-        if (mAttachInfo.mHardwareRenderer != null && mAttachInfo.mHardwareRenderer.isEnabled()) {
+        if (mAttachInfo.mHardwareRenderer != null) {
             mAttachInfo.mHardwareRenderer.detachFunctor(functor);
         }
     }