Display WebView description in devtools

Fixed this issue by overriding GetDescription().

Bug: 1059071
Change-Id: I7def9efbf3b9ae1d86511b875b8e44af60c99a56
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2090727Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Tao Bai <michaelbai@chromium.org>
Cr-Commit-Position: refs/heads/master@{#747798}

content/browser/devtools/forwarding_agent_host.cc

@@ -63,4 +63,8 @@ base::TimeTicks ForwardingAgentHost::GetLastActivityTime() {
   return delegate_->GetLastActivityTime();
 }
 
+std::string ForwardingAgentHost::GetDescription() {
+  return delegate_->GetDescription();
+}
+
 }  // content

content/browser/devtools/forwarding_agent_host.h

@@ -36,6 +36,7 @@ class ForwardingAgentHost : public DevToolsAgentHostImpl {
   void Reload() override;
   bool Close() override;
   base::TimeTicks GetLastActivityTime() override;
+  std::string GetDescription() override;
 
   std::unique_ptr<DevToolsExternalAgentProxyDelegate> delegate_;
   DISALLOW_COPY_AND_ASSIGN(ForwardingAgentHost);