Add a finch experiment for different memory pressure management strategies in ChromeOS.

chromeos/chromeos_switches.cc

Index: chromeos/chromeos_switches.cc
diff --git a/chromeos/chromeos_switches.cc b/chromeos/chromeos_switches.cc
index 6ac7d2e345844d6598483c3b419c99e3294e5d26..e603cfe125bcd8d519022abafbca2864ab42b4f0 100644
--- a/chromeos/chromeos_switches.cc
+++ b/chromeos/chromeos_switches.cc
@@ -5,6 +5,7 @@
 #include "chromeos/chromeos_switches.h"
 
 #include "base/command_line.h"
+#include "base/metrics/field_trial.h"
 
 // TODO(rsorokin): alphabetize all of these switches so they
 // match the order from the .h file
@@ -224,6 +225,10 @@ const char kLoginUser[] = "login-user";
 // The memory pressure thresholds selection which is used to decide when a
 // memory pressure event needs to get fired.
 const char kMemoryPressureThresholds[] = "memory-pressure-thresholds";
+const char kConservativeThreshold[] = "conservative";
+const char kAggressiveCacheDiscardThreshold[] = "aggressive-cache-discard";
+const char kAggressiveTabDiscardThreshold[] = "aggressive-tab-discard";
+const char kAggressiveThreshold[] = "aggressive";
 
 // Enables natural scroll by default.
 const char kNaturalScrollDefault[] = "enable-natural-scroll-default";
@@ -313,25 +318,34 @@ bool WakeOnWifiEnabled() {
 
 base::MemoryPressureObserverChromeOS::MemoryPressureThresholds
 GetMemoryPressureThresholds() {
-  if (!base::CommandLine::ForCurrentProcess()->HasSwitch(
-          kMemoryPressureThresholds)) {

[Mr4D (OOO till 08-26), 2015/02/09 00:54:54]

The field trial code should go into the case that there is no switch specified.

The order is:
1. User settings are most important -> they cannot be overwritten.
2. Trials can be used if 1. does not exist.

-    return base::MemoryPressureObserverChromeOS::THRESHOLD_DEFAULT;
-  }
   const std::string option =
       base::CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
           kMemoryPressureThresholds);
-  if (option == "1") {
+  if (option == kConservativeThreshold)
     return base::MemoryPressureObserverChromeOS::THRESHOLD_CONSERVATIVE;
-  }
-  if (option == "2") {
+  if (option == kAggressiveCacheDiscardThreshold)
     return base::MemoryPressureObserverChromeOS::
         THRESHOLD_AGGRESSIVE_CACHE_DISCARD;
-  }
-  if (option == "3") {
+  if (option == kAggressiveTabDiscardThreshold)
     return base::MemoryPressureObserverChromeOS::
         THRESHOLD_AGGRESSIVE_TAB_DISCARD;
-  }
-  return base::MemoryPressureObserverChromeOS::THRESHOLD_AGGRESSIVE;
+  if (option == kAggressiveThreshold)
+    return base::MemoryPressureObserverChromeOS::THRESHOLD_AGGRESSIVE;
+
+  const std::string group_name =
+      base::FieldTrialList::FindFullName(kMemoryPressureThresholds);
+  if (group_name == kConservativeThreshold)
+    return base::MemoryPressureObserverChromeOS::THRESHOLD_CONSERVATIVE;
+  if (group_name == kAggressiveCacheDiscardThreshold)
+    return base::MemoryPressureObserverChromeOS::
+        THRESHOLD_AGGRESSIVE_CACHE_DISCARD;
+  if (group_name == kAggressiveTabDiscardThreshold)
+    return base::MemoryPressureObserverChromeOS::
+        THRESHOLD_AGGRESSIVE_TAB_DISCARD;
+  if (group_name == kAggressiveThreshold)
+    return base::MemoryPressureObserverChromeOS::THRESHOLD_AGGRESSIVE;
+
+  return base::MemoryPressureObserverChromeOS::THRESHOLD_DEFAULT;
 }
 
 }  // namespace switches