Fix stale key drawing

Bug: 6509479
Change-Id: I49988ac951f6b37b14192ef1113a0d668a84f1a2

java/src/com/android/inputmethod/keyboard/Keyboard.java

@@ -197,6 +197,20 @@ public class Keyboard {
         return null;
     }
 
+    public boolean hasKey(Key aKey) {
+        if (mKeyCache.containsKey(aKey)) {
+            return true;
+        }
+
+        for (final Key key : mKeys) {
+            if (key == aKey) {
+                mKeyCache.put(key.mCode, key);
+                return true;
+            }
+        }
+        return false;
+    }
+
     public static boolean isLetterCode(int code) {
         return code >= MINIMUM_LETTER_CODE;
     }

java/src/com/android/inputmethod/keyboard/KeyboardView.java

@@ -487,6 +487,9 @@ public class KeyboardView extends View implements PointerTracker.DrawingProxy {
         } else {
             // Draw invalidated keys.
             for (final Key key : mInvalidatedKeys) {
+                if (!mKeyboard.hasKey(key)) {
+                    continue;
+                }
                 final int x = key.mX + getPaddingLeft();
                 final int y = key.mY + getPaddingTop();
                 mInvalidatedKeysRect.set(x, y, x + key.mWidth, y + key.mHeight);