<webview> Implement clear http cache API.

components/web_cache/browser/web_cache_manager.cc

Index: components/web_cache/browser/web_cache_manager.cc
diff --git a/components/web_cache/browser/web_cache_manager.cc b/components/web_cache/browser/web_cache_manager.cc
index 4acd2097ac31a60b69eb732fcd0aecf2f49c9d6e..840b33e06146e222eef9c2150fb5029a9a817bab 100644
--- a/components/web_cache/browser/web_cache_manager.cc
+++ b/components/web_cache/browser/web_cache_manager.cc
@@ -324,6 +324,10 @@ void WebCacheManager::EnactStrategy(const AllocationStrategy& strategy) {
   }
 }
 
+void WebCacheManager::ClearCacheForProcess(int render_process_id) {
+  ClearRendererCache(std::set<int>({render_process_id}), INSTANTLY);
+}
+
 void WebCacheManager::ClearRendererCache(
     const std::set<int>& renderers,
     WebCacheManager::ClearCacheOccasion occasion) {