Revert of Use FrameIsAd to decide whether to isolate a frame in TopDocumentIsolation mode.

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 f78db0afa915e7f714535296520bebf6620e8cd6..1d842a1259631a4a190152611730dd92016ba99d 100644
--- a/content/public/common/content_features.cc
+++ b/content/public/common/content_features.cc
@@ -297,11 +297,6 @@
 const base::Feature kTopDocumentIsolation{"top-document-isolation",
                                           base::FEATURE_DISABLED_BY_DEFAULT};
 
-// Field trial param (see base::GetFieldTrialParamValueByFeature)
-// controlling the mode for selecting which subframes end in the TDI process.
-// Valid values are integers from the TopDocumentIsolationMode enum.
-const char kTopDocumentIsolationModeParam[] = "mode";
-
 // Enables touchpad and wheel scroll latching.
 const base::Feature kTouchpadAndWheelScrollLatching{
     "TouchpadAndWheelScrollLatching", base::FEATURE_DISABLED_BY_DEFAULT};