Adding MHTML support into Page Load Metrics

chrome/browser/page_load_metrics/page_load_metrics_observer.h

 // Copyright 2015 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.
 
 #ifndef CHROME_BROWSER_PAGE_LOAD_METRICS_PAGE_LOAD_METRICS_OBSERVER_H_
 #define CHROME_BROWSER_PAGE_LOAD_METRICS_PAGE_LOAD_METRICS_OBSERVER_H_
 
+#include <string>
+
 #include "base/macros.h"
 #include "base/optional.h"
 #include "chrome/common/page_load_metrics/page_load_timing.h"
 #include "content/public/browser/navigation_handle.h"
 #include "third_party/WebKit/public/platform/WebInputEvent.h"
 #include "url/gurl.h"
 
 namespace page_load_metrics {
 
 // This enum represents how a page load ends. If the action occurs before the
@@ skipping 216 matching lines @@
   // OnHidden is triggered when a page leaves the foreground. It does not fire
   // when a foreground page is permanently closed; for that, listen to
   // OnComplete instead.
   virtual ObservePolicy OnHidden(const PageLoadTiming& timing,
                                  const PageLoadExtraInfo& extra_info);
 
   // OnShown is triggered when a page is brought to the foreground. It does not
   // fire when the page first loads; for that, listen for OnStart instead.
   virtual ObservePolicy OnShown();
 
+  // Called before OnCommit. The observer should return whether it wishes to
+  // observe navigations whose main resource has MIME type |mine_type|. The
+  // default is to observe HTML and XHTML only. Note that PageLoadTrackers only
+  // track XHTML, HTML, and MHTML (related/multipart).
+  virtual ObservePolicy ShouldObserveMimeType(
+      const std::string& mime_type) const;
+
   // The callbacks below are only invoked after a navigation commits, for
   // tracked page loads. Page loads that don't meet the criteria for being
   // tracked at the time a navigation commits will not receive any of the
   // callbacks below.
 
   // OnTimingUpdate is triggered when an updated PageLoadTiming is
   // available. This method may be called multiple times over the course of the
   // page load. This method is currently only intended for use in testing. Most
   // implementers should implement one of the On* callbacks, such as
   // OnFirstContentfulPaint or OnDomContentLoadedEventStart. Please email
@@ skipping 72 matching lines @@
       const FailedProvisionalLoadInfo& failed_provisional_load_info,
       const PageLoadExtraInfo& extra_info) {}
 
   // Called whenever a request is loaded for this page load.
   virtual void OnLoadedResource(const ExtraRequestInfo& extra_request_info) {}
 };
 
 }  // namespace page_load_metrics
 
 #endif  // CHROME_BROWSER_PAGE_LOAD_METRICS_PAGE_LOAD_METRICS_OBSERVER_H_