Suppress spurious foreground/background notifications

components/page_load_metrics/browser/metrics_web_contents_observer.cc

 // 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.
 
 #include "components/page_load_metrics/browser/metrics_web_contents_observer.h"
 
 #include <utility>
 
 #include "base/location.h"
 #include "base/logging.h"
@@ skipping 141 matching lines @@
                            aborted_chain_size_);
       return;
     default:
       NOTREACHED();
       return;
   }
 }
 
 void PageLoadTracker::WebContentsHidden() {
   // Only log the first time we background in a given page load.
-  if (background_time_.is_null())
+  if (background_time_.is_null()) {
+    // Make sure we either started in the foreground and haven't been
+    // foregrounded yet, or started in the background and have already been
+    // foregrounded.
+    DCHECK_EQ(started_in_foreground_, foreground_time_.is_null());
     background_time_ = base::TimeTicks::Now();
+  }
 }
 
 void PageLoadTracker::WebContentsShown() {
   // Only log the first time we foreground in a given page load.
-  if (foreground_time_.is_null())
+  if (foreground_time_.is_null()) {
+    // Make sure we either started in the background and haven't been
+    // backgrounded yet, or started in the foreground and have already been
+    // backgrounded.
+    DCHECK_NE(started_in_foreground_, background_time_.is_null());
     foreground_time_ = base::TimeTicks::Now();
+  }
 }
 
 void PageLoadTracker::Commit(content::NavigationHandle* navigation_handle) {
   // TODO(bmcquade): To improve accuracy, consider adding commit time to
   // NavigationHandle. Taking a timestamp here should be close enough for now.
   commit_time_ = base::TimeTicks::Now();
   committed_url_ = navigation_handle->GetURL();
   for (const auto& observer : observers_) {
     observer->OnCommit(navigation_handle);
   }
@@ skipping 252 matching lines @@
     content::NavigationHandle* navigation_handle) {
   if (!navigation_handle->IsInMainFrame())
     return;
   auto it = provisional_loads_.find(navigation_handle);
   if (it == provisional_loads_.end())
     return;
   it->second->Redirect(navigation_handle);
 }
 
 void MetricsWebContentsObserver::WasShown() {
+  if (in_foreground_)
+    return;
   in_foreground_ = true;
   if (committed_load_)
     committed_load_->WebContentsShown();
   for (const auto& kv : provisional_loads_) {
     kv.second->WebContentsShown();
   }
 }
 
 void MetricsWebContentsObserver::WasHidden() {
+  if (!in_foreground_)
+    return;
   in_foreground_ = false;
   if (committed_load_)
     committed_load_->WebContentsHidden();
   for (const auto& kv : provisional_loads_) {
     kv.second->WebContentsHidden();
   }
 }
 
 // This will occur when the process for the main RenderFrameHost exits, either
 // normally or from a crash. We eagerly log data from the last committed load if
@@ skipping 89 matching lines @@
 
   if (!committed_load_->UpdateTiming(timing)) {
     // If the page load tracker cannot update its timing, something is wrong
     // with the IPC (it's from another load, or it's invalid in some other way).
     // We expect this to be a rare occurrence.
     RecordInternalError(ERR_BAD_TIMING_IPC);
   }
 }
 
 }  // namespace page_load_metrics