Remove unused block_mixed_plugin_content from RequestExtraData

I found a setter of block_mixed_plugin_content is not called from anywhere so
removed the param as preparation of Loader's Onion Soup.

Bug: 860403
Change-Id: I2a47e70f7c551727d918888977548142214b1725
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1883349Reviewed-by: Yutaka Hirano <yhirano@chromium.org>
Commit-Queue: Makoto Shimazu <shimazu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#709818}

content/renderer/loader/request_extra_data.h

@@ -55,14 +55,6 @@ class CONTENT_EXPORT RequestExtraData : public blink::WebURLRequest::ExtraData {
     navigation_response_override_ = std::move(response_override);
   }
 
-  // Copy of the settings value determining if mixed plugin content should be
-  // blocked.
-  bool block_mixed_plugin_content() const {
-    return block_mixed_plugin_content_;
-  }
-  void set_block_mixed_plugin_content(bool block_mixed_plugin_content) {
-    block_mixed_plugin_content_ = block_mixed_plugin_content;
-  }
   std::vector<std::unique_ptr<blink::URLLoaderThrottle>>
   TakeURLLoaderThrottles() {
     return std::move(url_loader_throttles_);
@@ -91,7 +83,6 @@ class CONTENT_EXPORT RequestExtraData : public blink::WebURLRequest::ExtraData {
   blink::WebString custom_user_agent_;
   std::unique_ptr<NavigationResponseOverrideParameters>
       navigation_response_override_;
-  bool block_mixed_plugin_content_ = false;
   std::vector<std::unique_ptr<blink::URLLoaderThrottle>> url_loader_throttles_;
   scoped_refptr<FrameRequestBlocker> frame_request_blocker_;
   bool allow_cross_origin_auth_prompt_ = false;

content/renderer/loader/web_url_request_util.cc

@@ -353,15 +353,9 @@ blink::mojom::RequestContextType GetRequestContextTypeForWebURLRequest(
 
 blink::WebMixedContentContextType GetMixedContentContextTypeForWebURLRequest(
     const WebURLRequest& request) {
-  bool block_mixed_plugin_content = false;
-  if (request.GetExtraData()) {
-    RequestExtraData* extra_data =
-        static_cast<RequestExtraData*>(request.GetExtraData());
-    block_mixed_plugin_content = extra_data->block_mixed_plugin_content();
-  }
-
   return blink::WebMixedContent::ContextTypeFromRequestContext(
-      request.GetRequestContext(), block_mixed_plugin_content);
+      request.GetRequestContext(),
+      /*strict_mixed_content_checking_for_plugin=*/false);
 }
 
 #undef STATIC_ASSERT_ENUM