Re-enable pre-read experiment as a finch field trial.

chrome/common/chrome_constants.cc

Index: chrome/common/chrome_constants.cc
diff --git a/chrome/common/chrome_constants.cc b/chrome/common/chrome_constants.cc
index e2565728a07a119082c4928959ef0ba5e6371c09..70dd97d4525f0a99805f44c42d61da96d2855643 100644
--- a/chrome/common/chrome_constants.cc
+++ b/chrome/common/chrome_constants.cc
@@ -230,14 +230,15 @@ const bool kEnableTouchIcon = false;
 
 const float kMaxShareOfExtensionProcesses = 0.30f;
 
+// This is used by the PreRead experiment.
+const char kPreReadEnvironmentVariable[] = "CHROME_PRE_READ_EXPERIMENT";
+
 #if defined(OS_LINUX)
 const int kLowestRendererOomScore = 300;
 const int kHighestRendererOomScore = 1000;
 #endif
 
 #if defined(OS_WIN)
-// This is used by the PreRead experiment.
-const char kPreReadEnvironmentVariable[] = "CHROME_PRE_READ_EXPERIMENT";
 // This is used by chrome in Windows 8 metro mode.
 const wchar_t kMetroChromeUserDataSubDir[] = L"Metro";
 const wchar_t kMetroNavigationAndSearchMessage[] =