Add position information for DrawViews.

Summary: Previously, we had no information about the positioning of the view until after we had attached it.  We have the position information attached to the shadow node, but this attaches it to the DrawView as well.  It also removes the need for AbstractClippingDrawCommand.

Reviewed By: ahmedre

Differential Revision: D3609092

ReactAndroid/src/main/java/com/facebook/react/flat/AbstractDrawCommand.java

@@ -19,8 +19,7 @@ import android.graphics.Color;
  * The idea is to be able to reuse unmodified objects when we build up DrawCommands before we ship
  * them to UI thread, but we can only do that if DrawCommands are immutable.
  */
-/* package */ abstract class AbstractDrawCommand extends AbstractClippingDrawCommand
-    implements Cloneable {
+/* package */ abstract class AbstractDrawCommand implements DrawCommand, Cloneable {
 
   private float mLeft;
   private float mTop;
@@ -28,10 +27,66 @@ import android.graphics.Color;
   private float mBottom;
   private boolean mFrozen;
 
+  protected boolean mNeedsClipping;
+  private float mClipLeft;
+  private float mClipTop;
+  private float mClipRight;
+  private float mClipBottom;
+
+  public final boolean clipBoundsMatch(
+      float clipLeft,
+      float clipTop,
+      float clipRight,
+      float clipBottom) {
+    return mClipLeft == clipLeft && mClipTop == clipTop
+        && mClipRight == clipRight && mClipBottom == clipBottom;
+  }
+
+  public final void setClipBounds(
+      float clipLeft,
+      float clipTop,
+      float clipRight,
+      float clipBottom) {
+    mClipLeft = clipLeft;
+    mClipTop = clipTop;
+    mClipRight = clipRight;
+    mClipBottom = clipBottom;
+    // We put this check here to not clip when we have the default [-infinity, infinity] bounds,
+    // since clipRect in those cases is essentially no-op anyway. This is needed to fix a bug that
+    // shows up during screenshot testing. Note that checking one side is enough, since if one side
+    // is infinite, all sides will be infinite, since we only set infinite for all sides at the
+    // same time - conversely, if one side is finite, all sides will be finite.
+    mNeedsClipping = mClipLeft != Float.NEGATIVE_INFINITY;
+  }
+
+  public final float getClipLeft() {
+    return mClipLeft;
+  }
+
+  public final float getClipTop() {
+    return mClipTop;
+  }
+
+  public final float getClipRight() {
+    return mClipRight;
+  }
+
+  public final float getClipBottom() {
+    return mClipBottom;
+  }
+
+  protected final void applyClipping(Canvas canvas) {
+    canvas.clipRect(mClipLeft, mClipTop, mClipRight, mClipBottom);
+  }
+
+  /**
+   * Don't override this unless you need to do custom clipping in a draw command.  Otherwise just
+   * override onPreDraw and onDraw.
+   */
   @Override
-  public final void draw(FlatViewGroup parent, Canvas canvas) {
+  public void draw(FlatViewGroup parent, Canvas canvas) {
     onPreDraw(parent, canvas);
-    if (shouldClip()) {
+    if (mNeedsClipping && shouldClip()) {
       canvas.save(Canvas.CLIP_SAVE_FLAG);
       applyClipping(canvas);
       onDraw(canvas);
@@ -67,8 +122,11 @@ import android.graphics.Color;
   /**
    * Updates boundaries of the AbstractDrawCommand and freezes it.
    * Will return a frozen copy if the current AbstractDrawCommand cannot be mutated.
+   *
+   * This should not be called on a DrawView, as the DrawView is modified on UI thread.  Use
+   * DrawView.collectDrawView instead to avoid race conditions.
    */
-  public final AbstractDrawCommand updateBoundsAndFreeze(
+  public AbstractDrawCommand updateBoundsAndFreeze(
       float left,
       float top,
       float right,