Don't try sending request to another frame in a navigated/deleted WebContents

In WebContents destructor, |find_request_manager_| is not reset but
FrameTreeNode destructor is trigerred, eventually causing calls to
FindRequestManager::SendFindRequest that will try to send a find request
to another frame in the same WebContents, which results in a crash.

There are also other cases where the WebContents is navigated away,
the window is closed, etc. where we also try sending to another frame
within that WebContents, even though we won't need it. This CL fixes
the crash, and the root cause will be explored and fixed in another CL.

Bug: 884679
Change-Id: I229f38a663d50b6a5e8e167ac0d483f9826a7f0b
Reviewed-on: https://chromium-review.googlesource.com/c/1242728
Commit-Queue: Rakina Zata Amni <[email protected]>
Reviewed-by: Alex Moshchuk <[email protected]>
Reviewed-by: Paul Meyer <[email protected]>
Cr-Commit-Position: refs/heads/master@{#607859}
diff --git a/content/browser/web_contents/web_contents_impl.cc b/content/browser/web_contents/web_contents_impl.cc
index 632eae8..80cb9a2c 100644
--- a/content/browser/web_contents/web_contents_impl.cc
+++ b/content/browser/web_contents/web_contents_impl.cc
@@ -650,6 +650,7 @@
   }
 
   color_chooser_.reset();
+  find_request_manager_.reset();
 
   NotifyDisconnected();