Timeline event for compiling irregexp bytecode.

runtime/vm/regexp_assembler_bytecode.cc

Index: runtime/vm/regexp_assembler_bytecode.cc
diff --git a/runtime/vm/regexp_assembler_bytecode.cc b/runtime/vm/regexp_assembler_bytecode.cc
index 9586aea84b2a07e0f0f2a84b1e3c81c6f65794f3..986c0e30fcc658f0ea5205bb0131a8084c578f74 100644
--- a/runtime/vm/regexp_assembler_bytecode.cc
+++ b/runtime/vm/regexp_assembler_bytecode.cc
@@ -12,6 +12,7 @@
 #include "vm/regexp.h"
 #include "vm/regexp_parser.h"
 #include "vm/regexp_interpreter.h"
+#include "vm/timeline.h"
 
 namespace dart {
 
@@ -460,6 +461,13 @@ static intptr_t Prepare(const RegExp& regexp,
 
   if (regexp.bytecode(is_one_byte) == TypedData::null()) {
     const String& pattern = String::Handle(zone, regexp.pattern());
+    NOT_IN_PRODUCT(TimelineDurationScope tds(Thread::Current(),
+                                             Timeline::GetCompilerStream(),
+                                             "CompileIrregexpBytecode");
+    if (tds.enabled()) {
+      tds.SetNumArguments(1);
+      tds.CopyArgument(0, "pattern", pattern.ToCString());
+    });  // !PRODUCT
 
     const bool multiline = regexp.is_multi_line();
     RegExpCompileData* compile_data = new(zone) RegExpCompileData();