Cancel the post touch fling when new touch is registered

Summary:
This diff aims to fix an issue I found while working on T113264056. It's to address the [comment](https://www.internalfb.com/diff/D3207608 (https://github.com/facebook/react-native/commit/a3146e41a259175f0c79e3c213523a0fb21613d7)?dst_version_fbid=507451319451602&transaction_fbid=1615731455398227) in an old diff D3207608 (https://github.com/facebook/react-native/commit/a3146e41a259175f0c79e3c213523a0fb21613d7). That issue begins to surface after I made the change in the next diff, which is discussed in detail in the task description (T113385381).

The fix here is to cancel the post touch processing when a new touch down is received. This should've cancel any previous post touch processing as the new touch should take full control of scrolling.

Changelog:
[Android][Fixed] - Cancel post touch process when new touch is received

Reviewed By: javache

Differential Revision: D34627330

fbshipit-source-id: 1fb8cfc1a4d94349b5290915a0a9f190186f2af3

ReactAndroid/src/main/java/com/facebook/react/views/scroll/ReactHorizontalScrollView.java

@@ -531,7 +531,7 @@ public class ReactHorizontalScrollView extends HorizontalScrollView
     }
 
     mVelocityHelper.calculateVelocity(ev);
-    int action = ev.getAction() & MotionEvent.ACTION_MASK;
+    int action = ev.getActionMasked();
     if (action == MotionEvent.ACTION_UP && mDragging) {
       ReactScrollViewHelper.updateFabricScrollState(this);
 
@@ -544,6 +544,10 @@ public class ReactHorizontalScrollView extends HorizontalScrollView
       handlePostTouchScrolling(Math.round(velocityX), Math.round(velocityY));
     }
 
+    if (action == MotionEvent.ACTION_DOWN) {
+      cancelPostTouchScrolling();
+    }
+
     return super.onTouchEvent(ev);
   }
 
@@ -821,6 +825,12 @@ public class ReactHorizontalScrollView extends HorizontalScrollView
         this, mPostTouchRunnable, ReactScrollViewHelper.MOMENTUM_DELAY);
   }
 
+  private void cancelPostTouchScrolling() {
+    if (mPostTouchRunnable != null) {
+      removeCallbacks(mPostTouchRunnable);
+    }
+  }
+
   private int predictFinalScrollPosition(int velocityX) {
     // predict where a fling would end up so we can scroll to the nearest snap offset
     final int maximumOffset = Math.max(0, computeHorizontalScrollRange() - getWidth());

ReactAndroid/src/main/java/com/facebook/react/views/scroll/ReactScrollView.java

@@ -369,7 +369,7 @@ public class ReactScrollView extends ScrollView
     }
 
     mVelocityHelper.calculateVelocity(ev);
-    int action = ev.getAction() & MotionEvent.ACTION_MASK;
+    int action = ev.getActionMasked();
     if (action == MotionEvent.ACTION_UP && mDragging) {
       ReactScrollViewHelper.updateFabricScrollState(this);
 
@@ -382,6 +382,10 @@ public class ReactScrollView extends ScrollView
       handlePostTouchScrolling(Math.round(velocityX), Math.round(velocityY));
     }
 
+    if (action == MotionEvent.ACTION_DOWN) {
+      cancelPostTouchScrolling();
+    }
+
     return super.onTouchEvent(ev);
   }
 
@@ -611,6 +615,12 @@ public class ReactScrollView extends ScrollView
         this, mPostTouchRunnable, ReactScrollViewHelper.MOMENTUM_DELAY);
   }
 
+  private void cancelPostTouchScrolling() {
+    if (mPostTouchRunnable != null) {
+      removeCallbacks(mPostTouchRunnable);
+    }
+  }
+
   private int predictFinalScrollPosition(int velocityY) {
     // predict where a fling would end up so we can scroll to the nearest snap offset
     // TODO(T106335409): Existing prediction still uses overscroller. Consider change this to use