[debug] mark more unused debug API as deprecated.

src/debug/debug.cc

Index: src/debug/debug.cc
diff --git a/src/debug/debug.cc b/src/debug/debug.cc
index 30fef70ec7fdf587f9df3212809bf4f052565837..c0420a273fbf030439dc4471a3daa66091026e8a 100644
--- a/src/debug/debug.cc
+++ b/src/debug/debug.cc
@@ -1773,11 +1773,6 @@ void Debug::OnCompileError(Handle<Script> script) {
 }
 
 
-void Debug::OnBeforeCompile(Handle<Script> script) {
-  ProcessCompileEvent(v8::BeforeCompile, script);
-}
-
-
 // Handle debugger actions when a new script is compiled.
 void Debug::OnAfterCompile(Handle<Script> script) {
   ProcessCompileEvent(v8::AfterCompile, script);