DevTools: stop idleness detector when pending navigation commits

This patch stops indleness detector when a new document gets committed.
This makes sure that networkIdle events for the previous document don't
come for the newly committed one.

Drive-by: cleanup test.

R=pfeldman

Change-Id: Ia0cbcbbda31e07957867c53641649dd80091281e
Reviewed-on: https://chromium-review.googlesource.com/745388Reviewed-by: Pavel Feldman <pfeldman@chromium.org>
Commit-Queue: Andrey Lushnikov <lushnikov@chromium.org>
Cr-Commit-Position: refs/heads/master@{#512760}

third_party/WebKit/LayoutTests/http/tests/inspector-protocol/page/page-lifecycleEvents.js

@@ -7,15 +7,13 @@
   var events = [];
   dp.Page.onLifecycleEvent(result => {
     events.push(result.params.name);
-    if (events.includes('networkIdle') && events.includes('networkAlmostIdle')) {
+    if (events.includes('networkIdle')) {
+      // 'load' can come before 'DOMContentLoaded'
       events.sort();
       testRunner.log(events);
       testRunner.completeTest();
     }
   });
 
-  // It's possible for Blink to finish the load and run out of tasks before
-  // network idle lifecycle events are generated.  Add a timeout
-  // greater than the network quiet window to guarantee that those events fire.
-  dp.Page.navigate({url: "data:text/html,Hello! <script>setTimeout(() => {}, 2000);</script>"});
+  dp.Page.navigate({url: "data:text/html,Hello!"});
 })

third_party/WebKit/Source/core/loader/IdlenessDetector.cpp

@@ -20,6 +20,8 @@ void IdlenessDetector::Shutdown() {
 }
 
 void IdlenessDetector::WillCommitLoad() {
+  network_2_quiet_ = -1;
+  network_0_quiet_ = -1;
   network_2_quiet_start_time_ = 0;
   network_0_quiet_start_time_ = 0;
 }