Add WARN_UNUSED_RESULT to base::Time methods that return bool.

components/nacl/renderer/ppb_nacl_private_impl.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/nacl/renderer/ppb_nacl_private.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <memory>
@@ skipping 1605 matching lines @@
     expected_content_length_ = response.expectedContentLength();
 
     // Defer loading after receiving headers. This is because we may already
     // have a cached translated nexe, so check for that now.
     url_loader_->setDefersLoading(true);
 
     std::string etag = response.httpHeaderField("etag").utf8();
     std::string last_modified =
         response.httpHeaderField("last-modified").utf8();
     base::Time last_modified_time;
-    base::Time::FromString(last_modified.c_str(), &last_modified_time);
+    ignore_result(
+        base::Time::FromString(last_modified.c_str(), &last_modified_time));

[digit1, 2017/01/03 15:29:13]

note: I'm not sure this is the right thing to do here. What could be the impact
of an invalid modified-time string here? It looks like the extracted base::Time
value is stored in a cache node. So the worst that could happen would be to
force too many re-downloads of a resource. However that's my very superficial
view of the code. Would love to have a better opinion on this, and be able to
add a comment here explaining why it's ok.

At least the change doesn't change runtime behaviour.

 
     bool has_no_store_header = false;
     std::string cache_control =
         response.httpHeaderField("cache-control").utf8();
 
     for (const std::string& cur : base::SplitString(
              cache_control, ",", base::TRIM_WHITESPACE, base::SPLIT_WANT_ALL)) {
       if (base::ToLowerASCII(cur) == "no-store")
         has_no_store_header = true;
     }
@@ skipping 100 matching lines @@
   // Mark the request as requesting a PNaCl bitcode file,
   // so that component updater can detect this user action.
   url_request.addHTTPHeaderField(
       blink::WebString::fromUTF8("Accept"),
       blink::WebString::fromUTF8("application/x-pnacl, */*"));
   url_request.setRequestContext(blink::WebURLRequest::RequestContextObject);
   downloader->Load(url_request);
 }
 
 }  // namespace nacl