Releasing lock even if exception is thrown.

However, the whole method needs to be reviewed. It still has several
locking/unlocking places not tied together by try-finally construct,
but they cannot be fixed without deeper understanding.

Change-Id: Iaaf87568d585327654be409377b6d57a1da135eb

Author: Jozef BABJAK

core/java/android/view/ViewRoot.java

@@ -1065,10 +1065,11 @@ private void performTraversals() {
                         }
                     }
                     mSurfaceHolder.mSurfaceLock.lock();
-                    // Make surface invalid.
-                    //mSurfaceHolder.mSurface.copyFrom(mSurface);
-                    mSurfaceHolder.mSurface = new Surface();
-                    mSurfaceHolder.mSurfaceLock.unlock();
+                    try {
+                        mSurfaceHolder.mSurface = new Surface();
+                    } finally {
+                        mSurfaceHolder.mSurfaceLock.unlock();
+                    }
                 }
             }