Get signals working in the EXTRA_DATA section of MHTML

chrome/browser/android/offline_pages/prerendering_loader.cc

Index: chrome/browser/android/offline_pages/prerendering_loader.cc
diff --git a/chrome/browser/android/offline_pages/prerendering_loader.cc b/chrome/browser/android/offline_pages/prerendering_loader.cc
index 0b2f878764963cadf74a4cf1ec95240527f95c2f..d4c5482c73b6674e78209c4f3154c9ba5489da57 100644
--- a/chrome/browser/android/offline_pages/prerendering_loader.cc
+++ b/chrome/browser/android/offline_pages/prerendering_loader.cc
@@ -8,6 +8,7 @@
 #include "base/logging.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/threading/thread_task_runner_handle.h"
+#include "base/time/time.h"
 #include "chrome/browser/profiles/profile.h"
 #include "content/public/browser/browser_context.h"
 #include "content/public/browser/browser_thread.h"
@@ -88,6 +89,14 @@ PrerenderingLoader::~PrerenderingLoader() {
   CancelPrerender();
 }
 
+void PrerenderingLoader::AddLoadingSignal(const char* signal_name) {
+  std::string signal(signal_name);
+  signal += ": ";
+  // We need a time in milliseconds, and JavaTime provides that.
+  signal += std::to_string(base::Time::Now().ToJavaTime());

[Dmitry Titov, 2017/03/29 18:53:06]

this is not using ToJavaTime() for what it is intended. 
Not sure why we need a wall clock timestamps BTW. Isn't it a delay from the
navigation that you want? If so, it'd be more straightforward to snapshot a
TickTime at the start and then compute TimeDeltas and use its ToMilliseconds
method. 

[Pete Williamson, 2017/03/29 22:05:42]

Reading the descriptions at the top of time.h, it says that TimeTicks may stand
still if the computer is suspended.  I'm not sure what "suspended" means here,
and was concerned that it might consider running in background as "suspended".

I've recoded using TimeTicks assuming that suspended means the CPU is not
running.

+  signal_data_.push_back(signal);
+}
+
 bool PrerenderingLoader::LoadPage(const GURL& url,
                                   const LoadPageCallback& load_done_callback,
                                   const ProgressCallback& progress_callback) {
@@ -98,6 +107,9 @@ bool PrerenderingLoader::LoadPage(const GURL& url,
     return false;
   }
 
+  // Add this signal to signal_data_.
+  AddLoadingSignal("StartLoading");
+
   // Create a WebContents instance to define and hold a SessionStorageNamespace
   // for this load request.
   DCHECK(!session_contents_.get());
@@ -152,6 +164,9 @@ void PrerenderingLoader::OnPrerenderStopLoading() {
   // Inform SnapshotController of OnLoad event so it can determine
   // when to consider it really LOADED.
   snapshot_controller_->DocumentOnLoadCompletedInMainFrame();
+
+  // Add this signal to signal_data_.
+  AddLoadingSignal("OnLoad");
 }
 
 void PrerenderingLoader::OnPrerenderDomContentLoaded() {
@@ -168,6 +183,9 @@ void PrerenderingLoader::OnPrerenderDomContentLoaded() {
       // second delay from this event).
       snapshot_controller_->DocumentAvailableInMainFrame();
     }
+
+    // Add this signal to signal_data_.
+    AddLoadingSignal("OnDomContentLoaded");
   }
 }
 
@@ -183,6 +201,10 @@ void PrerenderingLoader::OnPrerenderNetworkBytesChanged(int64_t bytes) {
 
 void PrerenderingLoader::StartSnapshot() {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+
+  // Add this signal to signal_data_.
+  AddLoadingSignal("Snapshotting");
+
   HandleLoadEvent();
 }