Adding MHTML support into Page Load Metrics

chrome/browser/page_load_metrics/observers/previews_page_load_metrics_observer.cc

 // Copyright 2016 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 "chrome/browser/page_load_metrics/observers/previews_page_load_metrics_observer.h"
 
-#include <string>
-
 #include "base/optional.h"
 #include "base/time/time.h"
 #include "chrome/browser/page_load_metrics/page_load_metrics_util.h"
 #include "chrome/common/page_load_metrics/page_load_timing.h"
 #include "content/public/browser/navigation_handle.h"
 #include "content/public/browser/web_contents.h"
 
 #if defined(OS_ANDROID)
 #include "chrome/browser/android/offline_pages/offline_page_tab_helper.h"
 #endif  // defined(OS_ANDROID)
@@ skipping 24 matching lines @@
 PreviewsPageLoadMetricsObserver::~PreviewsPageLoadMetricsObserver() {}
 
 page_load_metrics::PageLoadMetricsObserver::ObservePolicy
 PreviewsPageLoadMetricsObserver::OnCommit(
     content::NavigationHandle* navigation_handle) {
   return IsOfflinePreview(navigation_handle->GetWebContents())
              ? CONTINUE_OBSERVING
              : STOP_OBSERVING;
 }
 
+page_load_metrics::PageLoadMetricsObserver::ObservePolicy
+PreviewsPageLoadMetricsObserver::ShouldObserveMimeType(
+    const std::string& mime_type) const {
+  // Support observing HTML, XHTML, and MHTML. Offline previews are served as
+  // MHTML (multipart/related).
+  return mime_type == "text/html" || mime_type == "application/xhtml+xml" ||

[Bryan McQuade, 2017/02/21 18:50:15]

let's have this chain to the base class impl first, and if true, return true,
then also allow multipart/related:

if (PageLoadMetricsObserver::ShouldObserveMimeType(mime_type) ==
CONTINUE_OBSERVING)
  return CONTINUE_OBSERVING;
return mime_type == "multipart/related" ? CONTINUE_OBSERVING : STOP_OBSERVING;

or some variation of this.

+                 mime_type == "multipart/related"
+             ? CONTINUE_OBSERVING
+             : STOP_OBSERVING;
+}
+
 void PreviewsPageLoadMetricsObserver::OnDomContentLoadedEventStart(
     const page_load_metrics::PageLoadTiming& timing,
     const page_load_metrics::PageLoadExtraInfo& info) {
   if (!WasStartedInForegroundOptionalEventInForeground(
           timing.dom_content_loaded_event_start, info)) {
     return;
   }
   PAGE_LOAD_HISTOGRAM(
       internal::kHistogramOfflinePreviewsDOMContentLoadedEventFired,
       timing.dom_content_loaded_event_start.value());
@@ skipping 48 matching lines @@
 #if defined(OS_ANDROID)
   offline_pages::OfflinePageTabHelper* tab_helper =
       offline_pages::OfflinePageTabHelper::FromWebContents(web_contents);
   return tab_helper && tab_helper->IsShowingOfflinePreview();
 #else
   return false;
 #endif  // defined(OS_ANDROID)
 }
 
 }  // namespace previews