Model each Dart library as its own ScriptState when devtools are enabled.

Source/bindings/v8/custom/V8InjectedScriptHostCustom.cpp

Index: Source/bindings/v8/custom/V8InjectedScriptHostCustom.cpp
diff --git a/Source/bindings/v8/custom/V8InjectedScriptHostCustom.cpp b/Source/bindings/v8/custom/V8InjectedScriptHostCustom.cpp
index 933985e8e317ab47e7c87590f2e61d7adcc7b083..60c91363c3acc0fa4e3d81cc159a12a03801bd1b 100644
--- a/Source/bindings/v8/custom/V8InjectedScriptHostCustom.cpp
+++ b/Source/bindings/v8/custom/V8InjectedScriptHostCustom.cpp
@@ -38,6 +38,7 @@
 #include "V8NodeList.h"
 #include "V8Storage.h"
 #include "bindings/dart/DartHandleProxy.h"
+#include "bindings/dart/DartInjectedScriptHost.h"
 #include "bindings/v8/BindingSecurity.h"
 #include "bindings/v8/ScriptDebugServer.h"
 #include "bindings/v8/ScriptValue.h"
@@ -354,6 +355,14 @@ void V8InjectedScriptHost::evaluateMethodCustom(const v8::FunctionCallbackInfo<v
         return;
     }
 
+    // FIXME(dartbug.com/13804): refactor DartInjectedScriptHost to instead
+    // subclass InjectedScriptHost.
+    v8::Handle<v8::Value> dartResult = DartInjectedScriptHost::evaluateIfDartContext(args.Holder(), expression);
+    if (!dartResult.IsEmpty()) {
+        v8SetReturnValue(args, dartResult);
+        return;
+    }
+
     ASSERT(!v8::Context::GetCurrent().IsEmpty());
     v8::TryCatch tryCatch;
     v8::Handle<v8::Value> result = V8ScriptRunner::compileAndRunInternalScript(expression, args.GetIsolate());