Remove kLogPluginMessages flag as part of flag cleanup

content/public/common/content_switches.cc

Index: content/public/common/content_switches.cc
diff --git a/content/public/common/content_switches.cc b/content/public/common/content_switches.cc
index 44630613f35e1adaa7d80a509f0579642d69498f..9fd7199eed8abf0bb6adeb172225f918bd53b6fb 100644
--- a/content/public/common/content_switches.cc
+++ b/content/public/common/content_switches.cc
@@ -671,9 +671,6 @@ const char kLoggingLevel[]                  = "log-level";
 // Enables saving net log events to a file and sets the file name to use.
 const char kLogNetLog[]                     = "log-net-log";
 
-// Make plugin processes log their sent and received messages to VLOG(1).
-const char kLogPluginMessages[]             = "log-plugin-messages";
-
 // Sets the width and height above which a composited layer will get tiled.
 const char kMaxUntiledLayerHeight[]         = "max-untiled-layer-height";
 const char kMaxUntiledLayerWidth[]          = "max-untiled-layer-width";