Revert of Default enable main frame before activation and remove finch experiment.

content/public/common/content_features.cc

Index: content/public/common/content_features.cc
diff --git a/content/public/common/content_features.cc b/content/public/common/content_features.cc
index 7845009a52ec086e98e8880fd57d19bcd8c25faf..31d7aefcd42a438a13aaf29edcb7ea011fb83365 100644
--- a/content/public/common/content_features.cc
+++ b/content/public/common/content_features.cc
@@ -43,6 +43,12 @@
 // size of font.
 const base::Feature kFontCacheScaling{"FontCacheScaling",
                                       base::FEATURE_DISABLED_BY_DEFAULT};
+
+// Can main thread be pipelined with activation. Always disabled for devices
+// with fewer than 4 cores irrespective of this flag. Can also be overridden by
+// --enable(disable)-main-frame-before-activation command line flag.
+const base::Feature kMainFrameBeforeActivation{
+    "MainFrameBeforeActivation", base::FEATURE_DISABLED_BY_DEFAULT};
 
 // FeatureList definition for trials to enable the download button on
 // MediaDocument.