BackgroundExecutor: rename shouldCancel to shouldYield

Summary:
Changelog: [internal]

Name `shouldCancel` is misleading. It implies the commit is cancelled and doesn't happen.
`shouldYield` expresses the intent better, because the commit's changes do eventually reach mounting layer but the current commit is rather yielding to the next one.

Reviewed By: mdvacca

Differential Revision: D26126121

fbshipit-source-id: 18988f217cbc651f0010f6e2381682bdbaed8bd4

ReactCommon/react/renderer/mounting/ShadowTree.cpp

@@ -332,7 +332,7 @@ CommitStatus ShadowTree::tryCommit(
   auto newRootShadowNode = transaction(*oldRevision.rootShadowNode);
 
   if (!newRootShadowNode ||
-      (commitOptions.shouldCancel && commitOptions.shouldCancel())) {
+      (commitOptions.shouldYield && commitOptions.shouldYield())) {
     return CommitStatus::Cancelled;
   }
 
@@ -372,7 +372,7 @@ CommitStatus ShadowTree::tryCommit(
         *this, oldRootShadowNode, newRootShadowNode);
 
     if (!newRootShadowNode ||
-        (commitOptions.shouldCancel && commitOptions.shouldCancel())) {
+        (commitOptions.shouldYield && commitOptions.shouldYield())) {
       return CommitStatus::Cancelled;
     }
 

ReactCommon/react/renderer/mounting/ShadowTree.h

@@ -55,9 +55,10 @@ class ShadowTree final {
 
   struct CommitOptions {
     bool enableStateReconciliation{false};
-    // Lambda called inside `tryCommit`. If false is returned, commit is
-    // cancelled.
-    std::function<bool()> shouldCancel;
+
+    // Called during `tryCommit` phase. Returning true indicates current commit
+    // should yield to the next commit.
+    std::function<bool()> shouldYield;
   };
 
   /*

ReactCommon/react/renderer/uimanager/UIManagerBinding.cpp

@@ -458,15 +458,15 @@ jsi::Value UIManagerBinding::get(
             mostRecentSurfaceId = surfaceId;
             sharedUIManager->backgroundExecutor_(
                 [=, eventCount = completeRootEventCounter.load()] {
-                  auto shouldCancel = [=]() -> bool {
+                  auto shouldYield = [=]() -> bool {
                     // If `completeRootEventCounter` was incremented, another
                     // `completeSurface` call has been scheduled and current
-                    // `completeSurface` should be cancelled.
+                    // `completeSurface` should yield to it.
                     return completeRootEventCounter > eventCount &&
                         mostRecentSurfaceId == surfaceId;
                   };
                   sharedUIManager->completeSurface(
-                      surfaceId, shadowNodeList, {true, shouldCancel});
+                      surfaceId, shadowNodeList, {true, shouldYield});
                 });
 
             return jsi::Value::undefined();