Add ExecuteJavaScriptForTest and make all tests use it

android_webview/browser/aw_browser_main_parts.cc

Index: android_webview/browser/aw_browser_main_parts.cc
diff --git a/android_webview/browser/aw_browser_main_parts.cc b/android_webview/browser/aw_browser_main_parts.cc
index 85fa1ea28c0b899fd84dcbfbe6980aece1830a01..4c28f1430ff94100d91522f069b6607b163bd930 100644
--- a/android_webview/browser/aw_browser_main_parts.cc
+++ b/android_webview/browser/aw_browser_main_parts.cc
@@ -19,6 +19,7 @@
 #include "base/files/file_path.h"
 #include "base/path_service.h"
 #include "content/public/browser/android/synchronous_compositor.h"
+#include "content/public/browser/render_frame_host.h"
 #include "content/public/browser/render_process_host.h"
 #include "content/public/common/content_client.h"
 #include "content/public/common/content_switches.h"
@@ -118,6 +119,8 @@ void AwBrowserMainParts::PreMainMessageLoopRun() {
     gfx::GLSurface::InitializeOneOff();
   }
 
+  content::RenderFrameHost::AllowInjectingJavaScriptForAndroidWebView();
+
   // This is needed for WebView Classic backwards compatibility
   // See crbug.com/298495
   content::SetMaxURLChars(20 * 1024 * 1024);