Refactor Attribute Processing (Step 1)

Summary: Concolidate the creation of the "update payload" into
ReactNativeAttributePayload which now has a create
and a diff version. The create version can be used by
both mountComponent and setNativeProps. This means that
diffRawProperties moves into ReactNativeAttributePayload.

Instead of storing previousFlattenedStyle as memoized
state in the component tree, I recalculate it every
time. This allows better use of the generational GC.
However, it is still probably a fairly expensive
technique so I will follow it up with a diff that
walks both nested array trees to do the diffing in a
follow up.

This is the first diff of several steps.

@​public

Reviewed By: @vjeux

Differential Revision: D2440644

fb-gh-sync-id: 1d0da4f6e2bf716f33e119df947c044abb918471

Libraries/ReactIOS/NativeMethodsMixin.js

@@ -13,6 +13,7 @@
 
 var NativeModules = require('NativeModules');
 var RCTUIManager = NativeModules.UIManager;
+var ReactNativeAttributePayload = require('ReactNativeAttributePayload');
 var TextInputState = require('TextInputState');
 
 var findNodeHandle = require('findNodeHandle');
@@ -65,52 +66,15 @@ var NativeMethodsMixin = {
    * next render, they will remain active.
    */
   setNativeProps: function(nativeProps: Object) {
-    // nativeProps contains a style attribute that's going to be flattened
-    // and all the attributes expanded in place. In order to make this
-    // process do as few allocations and copies as possible, we return
-    // one if the other is empty. Only if both have values then we create
-    // a new object and merge.
-    var hasOnlyStyle = true;
-    for (var key in nativeProps) {
-      if (key !== 'style') {
-        hasOnlyStyle = false;
-        break;
-      }
-    }
-
-    var validAttributes = this.viewConfig.validAttributes;
-    var hasProcessedProps = false;
-    var processedProps = {};
-    for (var key in nativeProps) {
-      var process = validAttributes[key] && validAttributes[key].process;
-      if (process) {
-        hasProcessedProps = true;
-        processedProps[key] = process(nativeProps[key]);
-      }
-    }
-
-    var style = precomputeStyle(
-      flattenStyle(processedProps.style || nativeProps.style),
+    var updatePayload = ReactNativeAttributePayload.create(
+      nativeProps,
       this.viewConfig.validAttributes
     );
 
-    var props = null;
-    if (hasOnlyStyle) {
-      props = style;
-    } else {
-      props = nativeProps;
-      if (hasProcessedProps) {
-        props = mergeFast(props, processedProps);
-      }
-      if (style) {
-        props = mergeFast(props, style);
-      }
-    }
-
     RCTUIManager.updateView(
       findNodeHandle(this),
       this.viewConfig.uiViewClassName,
-      props
+      updatePayload
     );
   },