Add PostTask to starting spare renderer

Adds a configurable delay as well, but by default is zero so that the
spare renderer request happens in the next message loop.

Bug: 1115259
Change-Id: I787cd9cf60c517ea9ac83d28d0484928355007e0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2392766Reviewed-by: Tarun Bansal <tbansal@chromium.org>
Commit-Queue: Robert Ogden <robertogden@chromium.org>
Cr-Commit-Position: refs/heads/master@{#804430}

chrome/browser/navigation_predictor/navigation_predictor_renderer_warmup_client.cc

@@ -7,13 +7,17 @@
 #include <algorithm>
 #include <vector>
 
+#include "base/bind.h"
 #include "base/feature_list.h"
 #include "base/metrics/field_trial_params.h"
 #include "base/system/sys_info.h"
+#include "base/task/post_task.h"
 #include "base/time/default_tick_clock.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/search_engines/template_url_service_factory.h"
 #include "components/search_engines/template_url_service.h"
+#include "content/public/browser/browser_task_traits.h"
+#include "content/public/browser/browser_thread.h"
 #include "content/public/browser/render_process_host.h"
 #include "url/gurl.h"
 #include "url/origin.h"
@@ -58,7 +62,12 @@ NavigationPredictorRendererWarmupClient::
           base::GetFieldTrialParamByFeatureAsInt(
               kNavigationPredictorRendererWarmup,
               "cooldown_duration_ms",
-              60 * 1000))) {
+              60 * 1000))),
+      renderer_warmup_delay_(base::TimeDelta::FromMilliseconds(
+          base::GetFieldTrialParamByFeatureAsInt(
+              kNavigationPredictorRendererWarmup,
+              "renderer_warmup_delay_ms",
+              0))) {
   if (clock) {
     tick_clock_ = clock;
   } else {
@@ -197,5 +206,10 @@ void NavigationPredictorRendererWarmupClient::RecordMetricsAndMaybeDoWarmup() {
     return;
   }
 
-  DoRendererWarmpup();
+  content::GetUIThreadTaskRunner({})->PostDelayedTask(
+      FROM_HERE,
+      base::BindOnce(
+          &NavigationPredictorRendererWarmupClient::DoRendererWarmpup,
+          weak_factory_.GetWeakPtr()),
+      renderer_warmup_delay_);
 }

chrome/browser/navigation_predictor/navigation_predictor_renderer_warmup_client.h

@@ -6,6 +6,7 @@
 #define CHROME_BROWSER_NAVIGATION_PREDICTOR_NAVIGATION_PREDICTOR_RENDERER_WARMUP_CLIENT_H_
 
 #include "base/macros.h"
+#include "base/memory/weak_ptr.h"
 #include "base/optional.h"
 #include "base/time/tick_clock.h"
 #include "base/time/time.h"
@@ -88,6 +89,12 @@ class NavigationPredictorRendererWarmupClient
   // The amount of time to wait in-between doing a renderer warmup.
   const base::TimeDelta cooldown_duration_;
 
+  // The amount of time to delay starting a spare renderer.
+  const base::TimeDelta renderer_warmup_delay_;
+
+  base::WeakPtrFactory<NavigationPredictorRendererWarmupClient> weak_factory_{
+      this};
+
   DISALLOW_COPY_AND_ASSIGN(NavigationPredictorRendererWarmupClient);
 };
 

chrome/browser/navigation_predictor/navigation_predictor_renderer_warmup_client_unittest.cc

@@ -42,7 +42,10 @@ class TestNavigationPredictorRendererWarmupClient
       : NavigationPredictorRendererWarmupClient(profile, clock) {}
   ~TestNavigationPredictorRendererWarmupClient() override = default;
 
-  bool DidDoRendererWarmup() const { return did_renderer_warmup_; }
+  bool DidDoRendererWarmup() const {
+    base::RunLoop().RunUntilIdle();
+    return did_renderer_warmup_;
+  }
 
   void Reset() { did_renderer_warmup_ = false; }