[Contextual Search] Add Mojo-enabled API component.

chrome/renderer/contextualsearch/contextual_search_wrapper.cc

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/renderer/contextualsearch/contextual_search_wrapper.h"
+
+#include "base/strings/string_util.h"
+#include "gin/arguments.h"
+#include "gin/handle.h"
+#include "gin/object_template_builder.h"
+#include "third_party/WebKit/public/web/WebFrame.h"
+#include "third_party/WebKit/public/web/WebKit.h"
+#include "v8/include/v8.h"
+
+namespace search {
+
+static const char kContextualSearchObjectName[] = "contextualSearch";
+static const char kSetCaptionMethodName[] = "setCaption";
+
+// TODO(donnd): merge with the identical code in
+// chrome_object_extensions_utils (which chrome-android can't access).
+v8::Local<v8::Object> GetOrCreateChromeObject(v8::Isolate* isolate,
+                                              v8::Local<v8::Object> global) {
+  v8::Local<v8::Object> chrome;
+  v8::Local<v8::Value> chrome_value =
+      global->Get(gin::StringToV8(isolate, "chrome"));
+  if (chrome_value.IsEmpty() || !chrome_value->IsObject()) {
+    chrome = v8::Object::New(isolate);
+    global->Set(gin::StringToSymbol(isolate, "chrome"), chrome);
+  } else {
+    chrome = v8::Local<v8::Object>::Cast(chrome_value);
+  }
+  return chrome;
+}
+
+gin::WrapperInfo ContextualSearchWrapper::kWrapperInfo = {
+    gin::kEmbedderNativeGin};
+
+// static
+void ContextualSearchWrapper::Install(blink::WebFrame* frame) {
+  // NOTE: Installing new v8 functions that can access Chrome native code
+  // requires a security review!  We did an exahustive search for a better
+  // way to implement a communication channel between the page and Chrome,
+  // but found nothing better.
+  // TODO(donnd): use a better communication channel once that becomes
+  // available, e.g. navigator.connect API. See crbug.com/541683.
+  // TODO(donnd): refactor some of this boilerplate into a reusable
+  // method.  This was cribbed from MemoryBenchmarkingExtension.
+  v8::Isolate* isolate = blink::mainThreadIsolate();
+  v8::HandleScope handle_scope(isolate);
+  v8::Local<v8::Context> context = frame->mainWorldScriptContext();
+  if (context.IsEmpty())
+    return;
+
+  v8::Context::Scope context_scope(context);
+  gin::Handle<ContextualSearchWrapper> wrapper =
+      gin::CreateHandle(isolate, new ContextualSearchWrapper());
+  if (wrapper.IsEmpty())
+    return;
+
+  v8::Local<v8::Object> chrome =
+      GetOrCreateChromeObject(isolate, context->Global());
+  chrome->Set(gin::StringToV8(isolate, kContextualSearchObjectName),

[Donn Denman, 2015/10/28 00:26:56]

Johen, Can you tell me when this change to the chrome object gets undone or no
longer applies?  Specifically, are we modifying a copy of the chrome object
that's scoped to the given WebFrame, and so our changes will no longer apply
once that frame is destroyed?  Or should we be removing this setter at some
point?  E.g. we could instead pass in a RenderFrame and use a
RenderFrameObserver to unplug our API when the contents are destroyed or
didClearWindowObject is called, etc.

[jochen (gone - plz use gerrit), 2015/10/28 14:23:53]

we never reuse a context - if a frame is navigated, the context is destroyed.
(tl;dr no need to ever remove this)

+              wrapper.ToV8());
+}
+
+ContextualSearchWrapper::ContextualSearchWrapper() {}
+
+ContextualSearchWrapper::~ContextualSearchWrapper() {}
+
+gin::ObjectTemplateBuilder ContextualSearchWrapper::GetObjectTemplateBuilder(
+    v8::Isolate* isolate) {
+  return gin::Wrappable<ContextualSearchWrapper>::GetObjectTemplateBuilder(
+             isolate)
+      .SetMethod(kSetCaptionMethodName, &ContextualSearchWrapper::SetCaption);
+}
+
+// static
+void ContextualSearchWrapper::SetCaption(const std::string& caption) {
+  DVLOG(0) << "ctxs SetCaption: caption: " << caption;
+  // TODO(donnd): send the caption to the Browser!
+}
+
+}  // namespace search