[fix] Flow type checking and annotations

Fixes dozens of Flow errors; adds type annotations; marks more files for
Flow type checking. Fixes a bug in 'AppState'.

15 Flow errors remaining. Several React Native files are still not type
checked (e.g., PanResponder, Touchables)

Ref #465

src/modules/NativeMethodsMixin/index.js

@@ -15,6 +15,29 @@ import UIManager from '../../apis/UIManager';
 const hyphenPattern = /-([a-z])/g;
 const toCamelCase = str => str.replace(hyphenPattern, m => m[1].toUpperCase());
 
+type MeasureOnSuccessCallback = (
+  x: number,
+  y: number,
+  width: number,
+  height: number,
+  pageX: number,
+  pageY: number
+) => void;
+
+type MeasureInWindowOnSuccessCallback = (
+  x: number,
+  y: number,
+  width: number,
+  height: number
+) => void;
+
+type MeasureLayoutOnSuccessCallback = (
+  left: number,
+  top: number,
+  width: number,
+  height: number
+) => void;
+
 const NativeMethodsMixin = {
   /**
    * Removes focus from an input or view. This is the opposite of `focus()`.
@@ -34,7 +57,7 @@ const NativeMethodsMixin = {
   /**
    * Determines the position and dimensions of the view
    */
-  measure(callback) {
+  measure(callback: MeasureOnSuccessCallback) {
     UIManager.measure(findNodeHandle(this), callback);
   },
 
@@ -53,14 +76,18 @@ const NativeMethodsMixin = {
    * Note that these measurements are not available until after the rendering
    * has been completed.
    */
-  measureInWindow(callback) {
+  measureInWindow(callback: MeasureInWindowOnSuccessCallback) {
     UIManager.measureInWindow(findNodeHandle(this), callback);
   },
 
   /**
    * Measures the view relative to another view (usually an ancestor)
    */
-  measureLayout(relativeToNativeNode, onSuccess, onFail) {
+  measureLayout(
+    relativeToNativeNode: Object,
+    onSuccess: MeasureLayoutOnSuccessCallback,
+    onFail: () => void
+  ) {
     UIManager.measureLayout(findNodeHandle(this), relativeToNativeNode, onFail, onSuccess);
   },
 

src/modules/applyLayout/index.js

@@ -35,7 +35,7 @@ const safeOverride = (original, next) => {
   return next;
 };
 
-const applyLayout = Component => {
+const applyLayout = (Component: ReactClass<any>) => {
   const componentDidMount = Component.prototype.componentDidMount;
   const componentDidUpdate = Component.prototype.componentDidUpdate;
   const componentWillUnmount = Component.prototype.componentWillUnmount;

src/modules/applyNativeMethods/index.js

@@ -7,7 +7,7 @@
 
 import NativeMethodsMixin from '../NativeMethodsMixin';
 
-const applyNativeMethods = Component => {
+const applyNativeMethods = (Component: ReactClass<any>) => {
   Object.keys(NativeMethodsMixin).forEach(method => {
     if (!Component.prototype[method]) {
       Component.prototype[method] = NativeMethodsMixin[method];