Add cachebreaker to remote assets

Summary:
Changelog:
[Internal][Added] - Create a general utils for assets and add a cache breaker utility to set/get a urlparam for remote assets.

Reviewed By: motiz88

Differential Revision: D25521331

fbshipit-source-id: 042e52a27e826bc9993e80bc68cc6fc68abaf224

Libraries/Image/AssetSourceResolver.js

@@ -21,7 +21,7 @@ export type ResolvedAssetSource = {|
 import type {PackagerAsset} from '@react-native/assets/registry';
 
 const PixelRatio = require('../Utilities/PixelRatio');
-const pickScale = require('./AssetSourcePickScale');
+const {pickScale} = require('./AssetUtils');
 const Platform = require('../Utilities/Platform');
 
 const invariant = require('invariant');

Libraries/Image/AssetUtils.js

@@ -10,11 +10,12 @@
 
 'use strict';
 
-const PixelRatio = require('../Utilities/PixelRatio');
-function AssetSourcePickScale(
-  scales: Array<number>,
-  deviceScale?: number,
-): number {
+import PixelRatio from '../Utilities/PixelRatio';
+
+let cacheBreaker;
+let warnIfCacheBreakerUnset = true;
+
+export function pickScale(scales: Array<number>, deviceScale?: number): number {
   if (deviceScale == null) {
     deviceScale = PixelRatio.get();
   }
@@ -30,4 +31,16 @@ function AssetSourcePickScale(
   // in which case we default to 1
   return scales[scales.length - 1] || 1;
 }
-module.exports = AssetSourcePickScale;
+
+export function setUrlCacheBreaker(appendage: string) {
+  cacheBreaker = appendage;
+}
+
+export function getUrlCacheBreaker(): string {
+  if (__DEV__ && warnIfCacheBreakerUnset && cacheBreaker == null) {
+    warnIfCacheBreakerUnset = false;
+    console.warn('AssetUtils.getUrlCacheBreaker: Cache breaker value is unset');
+    return '';
+  }
+  return cacheBreaker;
+}

Libraries/Image/resolveAssetSource.js

@@ -14,7 +14,7 @@
 
 const AssetRegistry = require('@react-native/assets/registry');
 const AssetSourceResolver = require('./AssetSourceResolver');
-const AssetSourcePickScale = require('./AssetSourcePickScale');
+const {pickScale} = require('./AssetUtils');
 
 import type {ResolvedAssetSource} from './AssetSourceResolver';
 
@@ -106,5 +106,5 @@ function resolveAssetSource(source: any): ?ResolvedAssetSource {
 }
 
 module.exports = resolveAssetSource;
-module.exports.pickScale = AssetSourcePickScale;
+module.exports.pickScale = pickScale;
 module.exports.setCustomSourceTransformer = setCustomSourceTransformer;