Remove most native WebContents references from Java

chrome/browser/prerender/external_prerender_handler_android.h

Index: chrome/browser/prerender/external_prerender_handler_android.h
diff --git a/chrome/browser/prerender/external_prerender_handler_android.h b/chrome/browser/prerender/external_prerender_handler_android.h
index 6009ddfbd1547adacb1f02fdd7f2c72b0b2acf64..d4d2995e5110f5b3711426770d2f2c8fd26e96aa 100644
--- a/chrome/browser/prerender/external_prerender_handler_android.h
+++ b/chrome/browser/prerender/external_prerender_handler_android.h
@@ -23,14 +23,14 @@ class PrerenderHandle;
 // A class for handling external prerender requests from other applications.
 class ExternalPrerenderHandlerAndroid {
  public:
-  explicit ExternalPrerenderHandlerAndroid();
+  ExternalPrerenderHandlerAndroid();
 
   // Add a prerender with the given url and referrer on the PrerenderManager of
   // the given profile. This is restricted to a single prerender at a time.
   bool AddPrerender(JNIEnv* env,
                     jobject obj,
                     jobject profile,
-                    jlong web_content_ptr,
+                    jobject jweb_contents,
                     jstring url,
                     jstring referrer,
                     jint width,