Gate Android drag and drop feature with a flag.

content/browser/android/content_view_core_impl.cc

Index: content/browser/android/content_view_core_impl.cc
diff --git a/content/browser/android/content_view_core_impl.cc b/content/browser/android/content_view_core_impl.cc
index 23708d9e4f9054cc2e2c0060204b85ad33921986..8eacd0d1d87ba68f21a8b3937a4b82ebb86666cc 100644
--- a/content/browser/android/content_view_core_impl.cc
+++ b/content/browser/android/content_view_core_impl.cc
@@ -58,6 +58,7 @@
 #include "ui/android/view_android.h"
 #include "ui/android/window_android.h"
 #include "ui/base/clipboard/clipboard.h"
+#include "ui/base/ui_base_switches_util.h"
 #include "ui/events/android/motion_event_android.h"
 #include "ui/events/blink/blink_event_util.h"
 #include "ui/events/event_utils.h"
@@ -1476,6 +1477,12 @@ void ContentViewCoreImpl::SetBackgroundOpaque(JNIEnv* env,
   }
 }
 
+bool ContentViewCoreImpl::IsTouchDragDropEnabled(
+    JNIEnv* env,
+    const base::android::JavaParamRef<jobject>& jobj) {
+  return switches::IsTouchDragDropEnabled();
+}
+
 void ContentViewCoreImpl::OnDragEvent(
     JNIEnv* env,
     const base::android::JavaParamRef<jobject>& jobj,