Fixes a reuse WebUI bug because of the incorrect shadowing of a boolean value.

This only affects PlzNavigate. When a same-site navigation should reuse the current WebUI, in RFHM::GetFrameHostForNavigation the (shadowing) method-local |should_reuse_web_ui_| would be set to true and the speculative WebUI would (correctly) not be created. But later on as the instance-level |should_reuse_web_ui_| defaults to false, RFHM::CommitPending would try to get the |speculative_web_ui_| which would not be set and *could* cause a crash. As of now the crash doesn't happen because CommitPending is not called when the current RFH is kept for the navigation.

BUG=376094

Review URL: https://codereview.chromium.org/1012863004

Cr-Commit-Position: refs/heads/master@{#322485}

content/browser/frame_host/render_frame_host_manager.cc

@@ -773,8 +773,8 @@ RenderFrameHostImpl* RenderFrameHostManager::GetFrameHostForNavigation(
     // As SiteInstances are the same, check if the WebUI should be reused.
     const NavigationEntry* current_navigation_entry =
         delegate_->GetLastCommittedNavigationEntryForRenderManager();
-    bool should_reuse_web_ui_ = ShouldReuseWebUI(current_navigation_entry,
-                                                 request.common_params().url);
+    should_reuse_web_ui_ = ShouldReuseWebUI(current_navigation_entry,
+                                            request.common_params().url);
     if (!should_reuse_web_ui_) {
       speculative_web_ui_ = CreateWebUI(request.common_params().url,
                                         request.bindings());