Cleanly handle excessively long JS source strings.

Source/bindings/core/v8/V8ScriptRunner.cpp

Index: Source/bindings/core/v8/V8ScriptRunner.cpp
diff --git a/Source/bindings/core/v8/V8ScriptRunner.cpp b/Source/bindings/core/v8/V8ScriptRunner.cpp
index 4bffe58068596dec34b9fbcd24f276be7341af11..937c3fec8b9c8d04e88406ae456e3cc3eb0c0b3d 100644
--- a/Source/bindings/core/v8/V8ScriptRunner.cpp
+++ b/Source/bindings/core/v8/V8ScriptRunner.cpp
@@ -355,11 +355,26 @@ PassOwnPtr<CompileFn> selectCompileFunction(ScriptResource* resource, ScriptStre
     ASSERT(!streamer->streamingSuppressed());
     return WTF::bind<v8::Isolate*, v8::Handle<v8::String>, v8::ScriptOrigin>(postStreamCompile, resource->cacheHandler(), streamer);
 }
+
+void throwSourceTooLargeException(const v8::FunctionCallbackInfo<v8::Value>& info)
+{
+    V8ThrowException::throwGeneralError(info.GetIsolate(), "Source file too large.");
+}
+
 } // namespace
 
 v8::Local<v8::Script> V8ScriptRunner::compileScript(const ScriptSourceCode& source, v8::Isolate* isolate, AccessControlStatus corsStatus, V8CacheOptions cacheOptions)
 {
-    return compileScript(v8String(isolate, source.source()), source.url(), source.sourceMapUrl(), source.startPosition(), isolate, source.resource(), source.streamer(), source.resource() ? source.resource()->cacheHandler() : nullptr, corsStatus, cacheOptions);
+    v8::Handle<v8::String> sourceAsV8String(v8String(isolate, source.source()));
+    if (sourceAsV8String.IsEmpty()) {
+        // String conversion fails when the source size exceeds the V8 string
+        // length of (currently) 256MB.
+        V8RecursionScope scope(isolate);
+        v8::Function::New(isolate, throwSourceTooLargeException)->Call(v8::Undefined(isolate), 0, 0);

[haraken, 2015/03/09 23:21:56]

Can we use a (already existing) helper function in V8ThrowException.h? We want
to centralize code that throws exceptions into V8ThrowException.h.

+        return v8::Local<v8::Script>();
+    }
+
+    return compileScript(sourceAsV8String, source.url(), source.sourceMapUrl(), source.startPosition(), isolate, source.resource(), source.streamer(), source.resource() ? source.resource()->cacheHandler() : nullptr, corsStatus, cacheOptions);
 }
 
 v8::Local<v8::Script> V8ScriptRunner::compileScript(v8::Handle<v8::String> code, const String& fileName, const String& sourceMapUrl, const TextPosition& scriptStartPosition, v8::Isolate* isolate, ScriptResource* resource, ScriptStreamer* streamer, CachedMetadataHandler* cacheHandler, AccessControlStatus corsStatus, V8CacheOptions cacheOptions, bool isInternalScript)