Pass main thread responsiveness threshold via Finch

content/renderer/input/main_thread_event_queue.cc

Index: content/renderer/input/main_thread_event_queue.cc
diff --git a/content/renderer/input/main_thread_event_queue.cc b/content/renderer/input/main_thread_event_queue.cc
index fe67fb2466804494a736e32a1b1aba62e2d960eb..92961c13079f52bea3eed03424ed13c8b47e662c 100644
--- a/content/renderer/input/main_thread_event_queue.cc
+++ b/content/renderer/input/main_thread_event_queue.cc
@@ -5,6 +5,8 @@
 #include "content/renderer/input/main_thread_event_queue.h"
 
 #include "base/metrics/histogram_macros.h"
+#include "base/strings/string_number_conversions.h"
+#include "components/variations/variations_associated_data.h"
 #include "content/common/input/event_with_latency_info.h"
 #include "content/common/input_messages.h"
 
@@ -78,7 +80,20 @@ MainThreadEventQueue::MainThreadEventQueue(
       handle_raf_aligned_mouse_input_(
           base::FeatureList::IsEnabled(features::kRafAlignedMouseInputEvents)),
       main_task_runner_(main_task_runner),
-      renderer_scheduler_(renderer_scheduler) {}
+      renderer_scheduler_(renderer_scheduler) {
+  if (enable_non_blocking_due_to_main_thread_responsiveness_flag_) {
+    std::string threshold = variations::GetVariationParamValueByFeature(
+        features::kMainThreadBusyScrollIntervention, "threshold");
+    int threshold_ms = 0;
+    base::StringToInt(threshold, &threshold_ms);
+    if (!threshold_ms) {
+      enable_non_blocking_due_to_main_thread_responsiveness_flag_ = false;

[dtapuska, 2016/12/16 19:59:46]

What about negative values? And StringToInt failing for overflow and underflow;
probably want it disabled in those cases no?

I'd expect this to be

if (!StringToInt(..) || threshold_ms <= 0)

[tdresser, 2016/12/16 20:12:08]

StringToInt saturates for overflow and underflow, which I think is fine. Added
handling for negative numbers.

+    } else {
+      main_thread_responsiveness_threshold_ =
+          base::TimeDelta::FromMilliseconds(threshold_ms);
+    }
+  }
+}
 
 MainThreadEventQueue::~MainThreadEventQueue() {}
 
@@ -133,7 +148,8 @@ bool MainThreadEventQueue::HandleEvent(
     if (enable_non_blocking_due_to_main_thread_responsiveness_flag_ &&
         touch_event->dispatchType == blink::WebInputEvent::Blocking) {
       bool passive_due_to_unresponsive_main =
-          renderer_scheduler_->MainThreadSeemsUnresponsive();
+          renderer_scheduler_->MainThreadSeemsUnresponsive(
+              main_thread_responsiveness_threshold_);
       if (passive_due_to_unresponsive_main) {
         touch_event->dispatchType = blink::WebInputEvent::
             ListenersForcedNonBlockingDueToMainThreadResponsiveness;