Implement Chrome Extension TabCapture API.

chrome/browser/extensions/api/tab_capture/tab_capture_api.cc

+// Copyright (c) 2012 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.
+
+// Implements the Chrome Extensions Tab Capture API.
+
+#include "chrome/browser/extensions/api/tab_capture/tab_capture_api.h"
+
+#include "base/stringprintf.h"
+#include "base/values.h"
+#include "chrome/browser/profiles/profile.h"
+#include "chrome/browser/extensions/api/tab_capture/tab_capture_registry.h"
+#include "chrome/browser/extensions/api/tab_capture/tab_capture_registry_factory.h"
+#include "chrome/browser/extensions/browser_event_router.h"
+#include "chrome/browser/extensions/event_names.h"
+#include "chrome/browser/extensions/extension_tab_id_map.h"
+
+namespace TabCapture = extensions::api::tab_capture;
+namespace GetCapturedTabs = TabCapture::GetCapturedTabs;
+
+namespace extensions {
+
+namespace {
+
+const char kPermissionError[] = "Extension does not have tabs permission";
+const char kErrorTabIdNotFound[] = "Could not find the specified tab.";
+const char kCapturingSameTab[] = "Cannot capture a tab with an active stream.";
+
+// Keys/values for media stream constraints.
+const char kMediaStreamSource[] = "chromeMediaSource";
+const char kMediaStreamSourceId[] = "chromeMediaSourceId";
+const char kMediaStreamSourceTab[] = "tab";
+
+}  // namespace
+
+TabCaptureCaptureFunction::TabCaptureCaptureFunction() { }
+TabCaptureCaptureFunction::~TabCaptureCaptureFunction() { }
+
+bool TabCaptureCaptureFunction::Prepare() {
+  if (!GetExtension()->HasAPIPermission(APIPermission::kTab)) {

[Aaron Boodman, 2012/10/16 04:19:27]

Two things:

(1) The 'tabs' permission is not the right level of access. Tabs permission just
means that the extension can see the URLs and titles in your browsing history.
This API also provides access to the content of those pages. So it should be
gated by 'host permissions' instead:
http://developer.chrome.com/extensions/manifest.html#permissions (the ones with
the URL patterns - we call these host permissions in the codebase).

(2) One interesting question is whether it would ever be useful for an extension
to be able to capture tab contents on some URLs but not others. The reason I ask
is that if that case is never interesting, then we can just make the tabCapture
permission 'imply' host permissions to all URLs. There are many other APIs we do
this with - for example the proxy API. You don't need to separately declare the
URLs you want access to in that case, we just assume it is all.

However, if it is the case that it would be useful to be able to capture on some
URLs but not others, then we could simply ask the developer to declare the
appropriate host permissions along with 'tabCapture'.

[justinlin, 2012/10/17 08:32:26]

Changed it back to kTabCapture permission as suggested in a different comment.

Interesting. Yes, I do think for this feature we should just imply "host
permissions" for all URLs by default. Actually, I'm not sure if it should even
require host permissions yet. The issue is that once the capture starts, the
user can navigate to any URL they want because the actual video capturing code
doesn't care about URL changes or checking permissions after it's started. I
think maybe it should just be a normal API permission. Also, this would
eventually just become a WebKit API (we are currently prototyping with
extensions), in which case we won't have the extension framework to check url
permissions.

+    error_ = kPermissionError;
+    return false;
+  }
+
+  params_ = TabCapture::Capture::Params::Create(*args_);
+  EXTENSION_FUNCTION_VALIDATE(params_.get());
+  return true;
+}
+
+void TabCaptureCaptureFunction::Work() {

[Aaron Boodman, 2012/10/16 04:19:27]

Wait a second... Why are you using AsyncApiFunction in the first place? There's
nothing in ::Work() that needs to be on the IO thread!

[justinlin, 2012/10/17 08:32:26]

Converting process and tab id to process and routing id needs to be done on the
IO thread: see ExtensionTabIdMap::GetProcessAndRoutingId or any method in that
class.

[Aaron Boodman, 2012/10/17 20:28:14]

You can get both the routing and process ID for a tab on the UI thread.

To get the routing ID:
UIThreadExtensionFunction::render_view_host()->GetRoutingID();

To get the process ID:
UIThreadExtensionFunction::render_view_host()->GetProcess()->GetID();

This is actually the typical way to work with these values in Chrome. The
ExtensionTabIdMap thing is a hack for certain functions that must do other work
on the IO thread.

[justinlin, 2012/10/17 23:41:48]

Done. OK, sorry for the contention surrounding AsyncApiFunction. I don't quite
want the current routing/render_process_id, but I want the one of the target
tab. Figured out how to do it. Looks better not as a SyncExtensionFunction.

+  ExtensionTabIdMap* tab_id_map = ExtensionTabIdMap::GetInstance();
+  int render_process_id = -1;
+  int routing_id = -1;
+  int tab_id = *params_->tab_id.get();
+  if (!tab_id_map ||
+      !tab_id_map->GetProcessAndRoutingId(tab_id,
+                                          &render_process_id,
+                                          &routing_id)) {
+    error_ = kErrorTabIdNotFound;
+    SetResult(base::Value::CreateIntegerValue(0));
+    return;
+  }
+
+  std::string device_id = base::StringPrintf("%i:%i", render_process_id,
+      routing_id);
+
+  request_key_ = device_id;
+  request_ =
+      (TabCaptureRegistry::TabCaptureRequest) { GetExtension()->id(), tab_id,

[Aaron Boodman, 2012/10/16 04:19:27]

Is the cast necessary? Seems like it wouldn't be.

[justinlin, 2012/10/17 08:32:26]

Done.

+          tab_capture::TAB_CAPTURE_TAB_CAPTURE_STATE_NONE };
+
+  bool audio = false;
+  bool video = false;
+  if (params_->options.get()) {
+    if (params_->options->audio.get()) {

[Aaron Boodman, 2012/10/16 04:19:27]

Nit: this brace is not necessary. It's optional though, if you prefer it.

[justinlin, 2012/10/17 08:32:26]

Done.

+      audio = *params_->options->audio.get();
+    }
+    if (params_->options->video.get()) {
+      video = *params_->options->video.get();
+    }
+  }
+
+  base::DictionaryValue* result = new base::DictionaryValue();

[Aaron Boodman, 2012/10/16 04:19:27]

JSON Schema Compiler generates structs you can use for the result too, instead
of doing this manual JSON stuff.

[justinlin, 2012/10/17 08:32:26]

These are sort of intermediate results that we are creating here, which the
tab_capture_custom_bindings.js will make use of. I don't think it makes sense to
put these structs in the IDL file, if that's what you meant.

[Aaron Boodman, 2012/10/17 20:28:14]

I see.

+  if (video) {
+    result->SetString(std::string("videoConstraints.mandatory.") +

[Aaron Boodman, 2012/10/16 04:19:27]

Question: why "constraints". Seem more like "details"?

[Aaron Boodman, 2012/10/16 04:22:28]

I take this back. 'constraints' is fine.

+        kMediaStreamSource, kMediaStreamSourceTab);
+    result->SetString(std::string("videoConstraints.mandatory.") +
+        kMediaStreamSourceId, device_id);
+  } else {
+    result->SetBoolean(std::string("videoConstraints"), false);
+  }
+
+  if (audio) {
+    result->SetString(std::string("audioConstraints.mandatory.") +
+        kMediaStreamSource, kMediaStreamSourceTab);
+    result->SetString(std::string("audioConstraints.mandatory.") +
+        kMediaStreamSourceId, device_id);
+  } else {
+    result->SetBoolean(std::string("audioConstraints"), false);
+  }
+
+  SetResult(result);
+}
+
+bool TabCaptureCaptureFunction::Respond() {
+  extensions::TabCaptureRegistry* registry =
+      extensions::TabCaptureRegistryFactory::GetForProfile(profile());
+  if (!request_key_.empty() && !registry->AddRequest(request_key_, request_)) {
+    error_ = kCapturingSameTab;
+    SetResult(base::Value::CreateIntegerValue(0));
+  }
+
+  return error_.empty();
+}
+
+bool TabCaptureGetCapturedTabsFunction::RunImpl() {
+  if (!GetExtension()->HasAPIPermission(APIPermission::kTab)) {
+    error_ = kPermissionError;
+    return false;
+  }
+
+  extensions::TabCaptureRegistry* registry =
+      extensions::TabCaptureRegistryFactory::GetForProfile(profile());
+
+  const TabCaptureRegistry::CaptureRequestList& captured_tabs =
+      registry->GetCapturedTabs(GetExtension()->id());
+
+  base::ListValue *list = new base::ListValue();
+  for (TabCaptureRegistry::CaptureRequestList::const_iterator it =
+       captured_tabs.begin(); it != captured_tabs.end(); it++) {
+    scoped_ptr<tab_capture::CaptureInfo> info(new tab_capture::CaptureInfo());
+    info->tab_id = it->tab_id;
+    info->status = it->status;
+    list->Append(info->ToValue().release());
+  }
+
+  SetResult(list);
+  return true;
+}
+
+}  // namespace extensions