Fix OomInterventionConfig default threshold

When no threshold is specified in FieldTrialParam, the default theshold was suppose to be 10% of system RAM, but actually it was set to 10 bytes.
blink_workload_threshold's unit is bytes.

Bug: 927599
Change-Id: I211347bdee5938b85ff27e29c694bf27906de6c0
Reviewed-on: https://chromium-review.googlesource.com/c/1448006Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Yuzu Saijo <yuzus@chromium.org>
Commit-Queue: Keishi Hattori <keishi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#628263}

chrome/browser/android/oom_intervention/oom_intervention_config.cc

@@ -138,11 +138,11 @@ OomInterventionConfig::OomInterventionConfig()
     is_swap_monitor_enabled_ = false;
     status = OomInterventionBrowserMonitorStatus::kEnabledWithNoSwap;
   }
-  // If no threshold is specified, set blink_workload_threshold to 10 by
-  // default, meaning that 10% of the RAM size is set to blink memory usage
-  // threshold to trigger intervention.
+  // If no threshold is specified, set blink_workload_threshold to 10% of the
+  // RAM size.
   if (!GetRendererMemoryThresholds(&renderer_detection_args_)) {
-    renderer_detection_args_->blink_workload_threshold = 10;
+    renderer_detection_args_->blink_workload_threshold =
+        base::SysInfo::AmountOfPhysicalMemory() * 0.1;
   }
 }