New tabCapture.captureOffscreenTab API, initially for Presentation API 1UA mode

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 <algorithm>
 #include <set>
 #include <string>
 #include <vector>
 
 #include "base/command_line.h"
 #include "base/strings/stringprintf.h"
 #include "base/values.h"
+#include "chrome/browser/extensions/api/tab_capture/offscreen_presentation.h"
 #include "chrome/browser/extensions/api/tab_capture/tab_capture_registry.h"
 #include "chrome/browser/extensions/extension_renderer_state.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/sessions/session_tab_helper.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/browser_finder.h"
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
+#include "chrome/common/chrome_switches.h"
 #include "content/public/browser/render_frame_host.h"
 #include "content/public/browser/render_process_host.h"
+#include "content/public/browser/web_contents.h"
 #include "extensions/common/features/feature.h"
 #include "extensions/common/features/feature_provider.h"
 #include "extensions/common/features/simple_feature.h"
 #include "extensions/common/permissions/permissions_data.h"
 #include "extensions/common/switches.h"
 
 using extensions::api::tab_capture::MediaStreamConstraint;
 
 namespace TabCapture = extensions::api::tab_capture;
 namespace GetCapturedTabs = TabCapture::GetCapturedTabs;
 
 namespace extensions {
 namespace {
 
 const char kCapturingSameTab[] = "Cannot capture a tab with an active stream.";
 const char kFindingTabError[] = "Error finding tab to capture.";
 const char kNoAudioOrVideo[] = "Capture failed. No audio or video requested.";
 const char kGrantError[] =
     "Extension has not been invoked for the current page (see activeTab "
     "permission). Chrome pages cannot be captured.";
 
+const char kCapturePresentationApiNotEnabled[] =
+    "Experimental capturePresentation API is not enabled.";
+const char kMissingTabCapturePermission[] =
+    "Extension manifest did not specify tabCapture permission.";
+const char kInvalidPresentationUrl[] =
+    "Invalid/Missing/Malformatted starting URL for presentation.";
+const char kMissingExtensionPage[] =
+    "Error finding extension page.";
+const char kTooManyPresentations[] =
+    "Extension has already started too many presentations.";
+const char kCapturingSamePresentation[] =
+    "Cannot capture the same presentation more than once.";
+
 // Keys/values for media stream constraints.
 const char kMediaStreamSource[] = "chromeMediaSource";
 const char kMediaStreamSourceId[] = "chromeMediaSourceId";
 const char kMediaStreamSourceTab[] = "tab";
 
 // Tab Capture-specific video constraint to enable automatic resolution/rate
 // throttling mode in the capture pipeline.
 const char kEnableAutoThrottlingKey[] = "enableAutoThrottling";
 
+bool OptionsSpecifyAudioOrVideo(const TabCapture::CaptureOptions& options) {
+  return (options.audio && *options.audio) || (options.video && *options.video);
+}
+
+bool IsAcceptablePresentationUrl(const GURL& url) {
+  return url.is_valid() && (url.SchemeIsHTTPOrHTTPS() || url.SchemeIs("data"));
+}
+
+void AddMediaStreamSourceOptions(TabCapture::CaptureOptions* options,
+                                 content::WebContents* target_contents) {
+  DCHECK(options);
+  DCHECK(target_contents);
+
+  // Create a constraints vector. We will modify all the constraints in this
+  // vector to append our chrome specific constraints.
+  std::vector<MediaStreamConstraint*> constraints;
+  if (options->audio.get() && *options->audio.get()) {

[Kevin M, 2015/06/29 22:17:02]

.get() isn't needed here or elsewhere in the function.

[miu, 2015/06/30 04:09:59]

Done.  In some places, it was still required.

+    if (!options->audio_constraints.get())
+      options->audio_constraints.reset(new MediaStreamConstraint);
+    constraints.push_back(options->audio_constraints.get());
+  }
+  bool enable_auto_throttling = false;
+  if (options->video.get() && *options->video.get()) {
+    if (options->video_constraints.get()) {
+      // Check for the Tab Capture-specific video constraint for enabling
+      // automatic resolution/rate throttling mode in the capture pipeline.  See
+      // implementation comments for content::WebContentsVideoCaptureDevice.
+      base::DictionaryValue& props =
+          options->video_constraints->mandatory.additional_properties;
+      if (!props.GetBooleanWithoutPathExpansion(
+              kEnableAutoThrottlingKey, &enable_auto_throttling)) {
+        enable_auto_throttling = false;
+      }
+      // Remove the key from the properties to avoid an "unrecognized
+      // constraint" error in the renderer.
+      props.RemoveWithoutPathExpansion(kEnableAutoThrottlingKey, nullptr);
+    } else {
+      options->video_constraints.reset(new MediaStreamConstraint);
+    }
+    constraints.push_back(options->video_constraints.get());
+  }
+
+  // Device id we use for Tab Capture.
+  content::RenderFrameHost* const main_frame = target_contents->GetMainFrame();
+  // TODO(miu): We should instead use a "randomly generated device ID" scheme,
+  // like that employed by the desktop capture API.  http://crbug.com/163100
+  const std::string device_id = base::StringPrintf(
+      "web-contents-media-stream://%i:%i%s",
+      main_frame->GetProcess()->GetID(),
+      main_frame->GetRoutingID(),
+      enable_auto_throttling ? "?throttling=auto" : "");
+
+  // Append chrome specific tab constraints.
+  for (MediaStreamConstraint* msc : constraints) {
+    base::DictionaryValue* constraint = &msc->mandatory.additional_properties;
+    constraint->SetString(kMediaStreamSource, kMediaStreamSourceTab);
+    constraint->SetString(kMediaStreamSourceId, device_id);
+  }
+}
+
+// Examine the minimum and maximum size constraints in |options| to determine
+// the page size for an off-screen presentation.
+gfx::Size DeterminePresentationSize(const TabCapture::CaptureOptions& options) {

[Kevin M, 2015/06/29 22:17:02]

Could this be unit tested to ensure that all the corner cases are correct? There
are a lot of conditionals here.

[miu, 2015/06/30 04:09:59]

Done.  Made this function a static class member to externalize it.

+  static const int kDefaultWidth = 1280;
+  static const int kDefaultHeight = 720;
+
+  if (!options.video_constraints)
+    return gfx::Size(kDefaultWidth, kDefaultHeight);
+
+  gfx::Size min_size;
+  int width = -1;
+  int height = -1;
+  const base::DictionaryValue& mandatory_properties =
+      options.video_constraints->mandatory.additional_properties;
+  if (mandatory_properties.GetInteger("maxWidth", &width) && width >= 0 &&
+      mandatory_properties.GetInteger("maxHeight", &height) && height >= 0) {
+    return gfx::Size(width, height);
+  }
+  if (mandatory_properties.GetInteger("minWidth", &width) && width >= 0 &&
+      mandatory_properties.GetInteger("minHeight", &height) && height >= 0) {
+    min_size.SetSize(width, height);
+  }
+
+  // Use optional size constraints if no mandatory ones were provided.
+  if (options.video_constraints->optional.get()) {
+    const base::DictionaryValue& optional_properties =
+        options.video_constraints->optional->additional_properties;
+    if (optional_properties.GetInteger("maxWidth", &width) && width >= 0 &&
+        optional_properties.GetInteger("maxHeight", &height) && height >= 0) {
+      if (min_size.IsEmpty()) {
+        return gfx::Size(width, height);
+      } else {
+        return gfx::Size(std::max(width, min_size.width()),
+                         std::max(height, min_size.height()));
+      }
+    }
+    if (min_size.IsEmpty() &&
+        optional_properties.GetInteger("minWidth", &width) && width >= 0 &&
+        optional_properties.GetInteger("minHeight", &height) && height >= 0) {
+      min_size.SetSize(width, height);
+    }
+  }
+
+  // No maximum size was provided, so just return the default size bounded by
+  // the minimum size.
+  return gfx::Size(std::max(kDefaultWidth, min_size.width()),
+                   std::max(kDefaultHeight, min_size.height()));
+}
+
 }  // namespace
 
 // Whitelisted extensions that do not check for a browser action grant because
 // they provide API's. If there are additional extension ids that need
 // whitelisting and are *not* the Chromecast extension, add them to a new
 // kWhitelist array.
 const char* const kChromecastExtensionIds[] = {
     "enhhojjnijigcajfphajepfemndkmdlo",  // Dev
     "pkedcjkdefgpdelpbcmbmeomcjbeemfm",  // Dogfood
     "fmfcbgogabcbclcofgocippekhfcmgfj",  // Staging
@@ skipping 30 matching lines @@
           SessionTabHelper::IdForTab(target_contents),
           APIPermission::kTabCaptureForTab) &&
       base::CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
           switches::kWhitelistedExtensionID) != extension_id &&
       !SimpleFeature::IsIdInArray(extension_id, kChromecastExtensionIds,
                                   arraysize(kChromecastExtensionIds))) {
     error_ = kGrantError;
     return false;
   }
 
-  // Create a constraints vector. We will modify all the constraints in this
-  // vector to append our chrome specific constraints.
-  std::vector<MediaStreamConstraint*> constraints;
-  bool has_audio = params->options.audio.get() && *params->options.audio.get();
-  bool has_video = params->options.video.get() && *params->options.video.get();
-
-  if (!has_audio && !has_video) {
+  if (!OptionsSpecifyAudioOrVideo(params->options)) {
     error_ = kNoAudioOrVideo;
     return false;
   }
 
-  if (has_audio) {
-    if (!params->options.audio_constraints.get())
-      params->options.audio_constraints.reset(new MediaStreamConstraint);
-
-    constraints.push_back(params->options.audio_constraints.get());
-  }
-
-  bool enable_auto_throttling = false;
-  if (has_video) {
-    if (params->options.video_constraints.get()) {
-      // Check for the Tab Capture-specific video constraint for enabling
-      // automatic resolution/rate throttling mode in the capture pipeline.  See
-      // implementation comments for content::WebContentsVideoCaptureDevice.
-      base::DictionaryValue& props =
-          params->options.video_constraints->mandatory.additional_properties;
-      if (!props.GetBooleanWithoutPathExpansion(
-              kEnableAutoThrottlingKey, &enable_auto_throttling)) {
-        enable_auto_throttling = false;
-      }
-      // Remove the key from the properties to avoid an "unrecognized
-      // constraint" error in the renderer.
-      props.RemoveWithoutPathExpansion(kEnableAutoThrottlingKey, nullptr);
-    } else {
-      params->options.video_constraints.reset(new MediaStreamConstraint);
-    }
-
-    constraints.push_back(params->options.video_constraints.get());
-  }
-
-  // Device id we use for Tab Capture.
-  content::RenderFrameHost* const main_frame = target_contents->GetMainFrame();
-  // TODO(miu): We should instead use a "randomly generated device ID" scheme,
-  // like that employed by the desktop capture API.  http://crbug.com/163100
-  const std::string device_id = base::StringPrintf(
-      "web-contents-media-stream://%i:%i%s",
-      main_frame->GetProcess()->GetID(),
-      main_frame->GetRoutingID(),
-      enable_auto_throttling ? "?throttling=auto" : "");
-
-  // Append chrome specific tab constraints.
-  for (std::vector<MediaStreamConstraint*>::iterator it = constraints.begin();
-       it != constraints.end(); ++it) {
-    base::DictionaryValue* constraint = &(*it)->mandatory.additional_properties;
-    constraint->SetString(kMediaStreamSource, kMediaStreamSourceTab);
-    constraint->SetString(kMediaStreamSourceId, device_id);
-  }
-
   TabCaptureRegistry* registry = TabCaptureRegistry::Get(GetProfile());
-  if (!registry->AddRequest(target_contents, extension_id)) {
+  if (!registry->AddRequest(target_contents, extension_id, false)) {
     error_ = kCapturingSameTab;
     return false;
   }
+  AddMediaStreamSourceOptions(&params->options, target_contents);
 
-  // Copy the result from our modified input parameters. This will be
-  // intercepted by custom bindings which will build and send the special
-  // WebRTC user media request.
+  // At this point, everything is set up in the browser process.  It's now up to
+  // the custom JS bindings in the renderer to request a MediaStream using
+  // navigator.webkitGetUserMedia().  The result dictionary, passed to
+  // SetResult() here, contains the extra "hidden options" that will allow the
+  // Chrome platform implementation for getUserMedia() to start the virtual
+  // audio/video capture devices and set up all the data flows.  The custom JS
+  // bindings can be found here:
+  // chrome/renderer/resources/extensions/tab_capture_custom_bindings.js
   base::DictionaryValue* result = new base::DictionaryValue();
   result->MergeDictionary(params->options.ToValue().get());
-
   SetResult(result);
   return true;
 }
 
 bool TabCaptureGetCapturedTabsFunction::RunSync() {
   TabCaptureRegistry* registry = TabCaptureRegistry::Get(GetProfile());
   base::ListValue* const list = new base::ListValue();
   if (registry)
     registry->GetCapturedTabs(extension()->id(), list);
   SetResult(list);
   return true;
 }
 
+bool TabCaptureCapturePresentationFunction::RunSync() {
+  scoped_ptr<TabCapture::CapturePresentation::Params> params =
+      TabCapture::CapturePresentation::Params::Create(*args_);
+  EXTENSION_FUNCTION_VALIDATE(params.get());
+
+  // One or both of two possible switches will enable this API for use.
+  if (!base::CommandLine::ForCurrentProcess()->HasSwitch(
+          ::switches::kEnableCapturePresentationApi) &&
+      !::switches::MediaRouterEnabled()) {
+    SetError(kCapturePresentationApiNotEnabled);
+    return false;
+  }
+
+  if (!extension()->permissions_data()->HasAPIPermission(
+          APIPermission::kTabCapture) &&
+      base::CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
+          switches::kWhitelistedExtensionID) != extension()->id() &&
+      !SimpleFeature::IsIdInArray(extension()->id(), kChromecastExtensionIds,
+                                  arraysize(kChromecastExtensionIds))) {
+    error_ = kMissingTabCapturePermission;
+    return false;
+  }
+
+  const GURL start_url(params->presentation_url);
+  if (!IsAcceptablePresentationUrl(start_url)) {
+    SetError(kInvalidPresentationUrl);
+    return false;
+  }
+
+  if (!OptionsSpecifyAudioOrVideo(params->options)) {
+    SetError(kNoAudioOrVideo);
+    return false;
+  }
+
+  content::WebContents* const extension_web_contents = GetSenderWebContents();
+  if (!extension_web_contents) {
+    SetError(kMissingExtensionPage);
+    return false;
+  }
+
+  OffscreenPresentation* const presentation =
+      OffscreenPresentationsOwner::Get(extension_web_contents)
+          ->FindOrStartPresentation(start_url,
+                                    params->presentation_id,
+                                    DeterminePresentationSize(params->options));
+  if (!presentation) {
+    SetError(kTooManyPresentations);
+    return false;
+  }
+  if (!TabCaptureRegistry::Get(browser_context())->AddRequest(
+          presentation->web_contents(), extension()->id(), true)) {
+    SetError(kCapturingSamePresentation);
+    return false;
+  }
+  AddMediaStreamSourceOptions(&params->options, presentation->web_contents());
+
+  // At this point, everything is set up in the browser process.  It's now up to
+  // the custom JS bindings in the renderer to complete the request.  See the
+  // comment at end of TabCaptureCaptureFunction::RunSync() for more details.
+  base::DictionaryValue* const result = new base::DictionaryValue();
+  result->MergeDictionary(params->options.ToValue().get());
+  SetResult(result);
+  return true;
+}
+
 }  // namespace extensions