metrics: Add leak detector controller in Chrome OS metrics system

chrome/common/chrome_features.cc

Index: chrome/common/chrome_features.cc
diff --git a/chrome/common/chrome_features.cc b/chrome/common/chrome_features.cc
index b571587be63827821488e5123875a7a0127a5a6a..418e283f57c6f67ac6e4d6dda49d4a8ce43ab12a 100644
--- a/chrome/common/chrome_features.cc
+++ b/chrome/common/chrome_features.cc
@@ -22,4 +22,11 @@ const base::Feature kLinuxObsoleteSystemIsEndOfTheLine{
     "LinuxObsoleteSystemIsEndOfTheLine", base::FEATURE_DISABLED_BY_DEFAULT};
 #endif
 
+#if defined(OS_CHROMEOS)
+// Runtime flag that indicates whether this leak detector should be enabled in
+// the current instance of Chrome.
+const base::Feature kRuntimeMemoryLeakDetector{
+    "RuntimeMemoryLeakDetector", base::FEATURE_DISABLED_BY_DEFAULT};
+#endif  // defined(OS_CHROMEOS)
+
 }  // namespace features