Adding PLM UMA for byte usage by load type

chrome/browser/page_load_metrics/observers/core_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_OBSERVERS_CORE_PAGE_LOAD_METRICS_OBSERVER_H_
 #define CHROME_BROWSER_PAGE_LOAD_METRICS_OBSERVERS_CORE_PAGE_LOAD_METRICS_OBSERVER_H_
 
 #include "chrome/browser/page_load_metrics/page_load_metrics_observer.h"
 
 namespace internal {
@@ skipping 36 matching lines @@
 extern const char kRapporMetricsNameCoarseTiming[];
 extern const char kHistogramFirstMeaningfulPaintStatus[];
 
 extern const char kHistogramFirstNonScrollInputAfterFirstPaint[];
 extern const char kHistogramFirstScrollInputAfterFirstPaint[];
 
 extern const char kHistogramTotalBytes[];
 extern const char kHistogramNetworkBytes[];
 extern const char kHistogramCacheBytes[];
 
+extern const char kHistogramLoadTypeTotalBytesForwardBack[];
+extern const char kHistogramLoadTypeNetworkBytesForwardBack[];
+extern const char kHistogramLoadTypeCacheBytesForwardBack[];
+
+extern const char kHistogramLoadTypeTotalBytesReload[];
+extern const char kHistogramLoadTypeNetworkBytesReload[];
+extern const char kHistogramLoadTypeCacheBytesReload[];
+
+extern const char kHistogramLoadTypeTotalBytesNewNavigation[];
+extern const char kHistogramLoadTypeNetworkBytesNewNavigation[];
+extern const char kHistogramLoadTypeCacheBytesNewNavigation[];
+
 extern const char kHistogramTotalCompletedResources[];
 extern const char kHistogramNetworkCompletedResources[];
 extern const char kHistogramCacheCompletedResources[];
 
 enum FirstMeaningfulPaintStatus {
   FIRST_MEANINGFUL_PAINT_RECORDED,
   FIRST_MEANINGFUL_PAINT_BACKGROUNDED,
   FIRST_MEANINGFUL_PAINT_DID_NOT_REACH_NETWORK_STABLE,
   FIRST_MEANINGFUL_PAINT_USER_INTERACTION_BEFORE_FMP,
   FIRST_MEANINGFUL_PAINT_DID_NOT_REACH_FIRST_CONTENTFUL_PAINT,
@@ skipping 86 matching lines @@
   bool received_scroll_input_after_first_paint_ = false;
 
   base::TimeTicks navigation_start_;
   base::TimeTicks first_user_interaction_after_first_paint_;
   base::TimeTicks first_paint_;
 
   DISALLOW_COPY_AND_ASSIGN(CorePageLoadMetricsObserver);
 };
 
 #endif  // CHROME_BROWSER_PAGE_LOAD_METRICS_OBSERVERS_CORE_PAGE_LOAD_METRICS_OBSERVER_H_