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

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

Index: chrome/browser/extensions/api/tab_capture/tab_capture_api.cc
diff --git a/chrome/browser/extensions/api/tab_capture/tab_capture_api.cc b/chrome/browser/extensions/api/tab_capture/tab_capture_api.cc
index 57605300a2b609207d9a78f950a03facd1e15ed9..ff336c9cdc3826d3844b1dc46d68ac147d45dcc0 100644
--- a/chrome/browser/extensions/api/tab_capture/tab_capture_api.cc
+++ b/chrome/browser/extensions/api/tab_capture/tab_capture_api.cc
@@ -6,6 +6,7 @@
 
 #include "chrome/browser/extensions/api/tab_capture/tab_capture_api.h"
 
+#include <algorithm>
 #include <set>
 #include <string>
 #include <vector>
@@ -13,6 +14,7 @@
 #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"
@@ -20,8 +22,10 @@
 #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"
@@ -43,6 +47,18 @@ const char kGrantError[] =
     "Extension has not been invoked for the current page (see activeTab "
     "permission). Chrome pages cannot be captured.";
 
+const char kNotWhitelistedForOffscreenTabApi[] =
+    "Extension is not whitelisted for use of the unstable, in-development "
+    "chrome.tabCapture.captureOffscreenTab API.";
+const char kInvalidStartUrl[] =
+    "Invalid/Missing/Malformatted starting URL for off-screen tab.";
+const char kMissingExtensionPage[] =
+    "tabCapture API was not invoked from an extension background page.";
+const char kTooManyOffscreenTabs[] =
+    "Extension has already started too many off-screen tabs.";
+const char kCapturingSameOffscreenTab[] =
+    "Cannot capture the same off-screen tab more than once.";
+
 // Keys/values for media stream constraints.
 const char kMediaStreamSource[] = "chromeMediaSource";
 const char kMediaStreamSourceId[] = "chromeMediaSourceId";
@@ -52,6 +68,70 @@ const char kMediaStreamSourceTab[] = "tab";
 // 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 IsAcceptableOffscreenTabUrl(const GURL& url) {
+  return url.is_valid() && (url.SchemeIsHTTPOrHTTPS() || url.SchemeIs("data"));
+}
+
+// Add Chrome-specific source identifiers to the MediaStreamConstraints objects
+// in |options| to provide references to the |target_contents| to be captured.
+void AddMediaStreamSourceConstraints(content::WebContents* target_contents,
+                                     TabCapture::CaptureOptions* options) {
+  DCHECK(options);
+  DCHECK(target_contents);
+
+  MediaStreamConstraint* constraints_to_modify[2] = { nullptr, nullptr };
+
+  if (options->audio && *options->audio) {
+    if (!options->audio_constraints)
+      options->audio_constraints.reset(new MediaStreamConstraint);
+    constraints_to_modify[0] = options->audio_constraints.get();
+  }
+
+  bool enable_auto_throttling = false;
+  if (options->video && *options->video) {
+    if (options->video_constraints) {
+      // 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_to_modify[1] = options->video_constraints.get();
+  }
+
+  // Format the device ID that references the target tab.
+  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_to_modify) {
+    if (!msc)
+      continue;
+    base::DictionaryValue* constraint = &msc->mandatory.additional_properties;
+    constraint->SetString(kMediaStreamSource, kMediaStreamSourceTab);
+    constraint->SetString(kMediaStreamSourceId, device_id);
+  }
+}
+
 }  // namespace
 
 // Whitelisted extensions that do not check for a browser action grant because
@@ -78,7 +158,7 @@ const char* const kMediaRouterExtensionIds[] = {
 bool TabCaptureCaptureFunction::RunSync() {
   scoped_ptr<api::tab_capture::Capture::Params> params =
       TabCapture::Capture::Params::Create(*args_);
-  EXTENSION_FUNCTION_VALIDATE(params.get());
+  EXTENSION_FUNCTION_VALIDATE(params);
 
   // Figure out the active WebContents and retrieve the needed ids.
   Browser* target_browser = chrome::FindAnyBrowser(
@@ -112,76 +192,30 @@ bool TabCaptureCaptureFunction::RunSync() {
     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)) {
+    // TODO(miu): Allow multiple consumers of single tab capture.
+    // http://crbug.com/535336
     error_ = kCapturingSameTab;
     return false;
   }
+  AddMediaStreamSourceConstraints(target_contents, &params->options);
 
-  // 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 extension's render process 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;
 }
@@ -195,4 +229,121 @@ bool TabCaptureGetCapturedTabsFunction::RunSync() {
   return true;
 }
 
+bool TabCaptureCaptureOffscreenTabFunction::RunSync() {
+  scoped_ptr<TabCapture::CaptureOffscreenTab::Params> params =
+      TabCapture::CaptureOffscreenTab::Params::Create(*args_);
+  EXTENSION_FUNCTION_VALIDATE(params);
+
+  // Make sure the extension is whitelisted for using this API, or this is a
+  // Canary/Dev-channel build of Chrome.
+  const bool is_whitelisted_extension =

[not at google - send to devlin, 2015/09/30 01:32:11]

A better way to whitelist is by adding a rule for tabCapture.captureOffscreenTab
to _api_features.json.

[miu, 2015/09/30 19:46:38]

Added a TODO for this.  The reason is that there is outside code (e.g., a CrOS
system tray UI feature) that references the extension ID arrays defined in this
file.  In other words, switching to using _api_features.json is a bit more work
than I'd feel comfortable doing in this CL.

+      base::CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
+          switches::kWhitelistedExtensionID) == extension()->id() ||
+      SimpleFeature::IsIdInArray(extension()->id(), kChromecastExtensionIds,
+                                 arraysize(kChromecastExtensionIds)) ||
+      SimpleFeature::IsIdInArray(extension()->id(), kMediaRouterExtensionIds,
+                                 arraysize(kMediaRouterExtensionIds));
+  if (!is_whitelisted_extension) {
+    error_ = kNotWhitelistedForOffscreenTabApi;
+    return false;
+  }
+
+  const GURL start_url(params->start_url);
+  if (!IsAcceptableOffscreenTabUrl(start_url)) {
+    SetError(kInvalidStartUrl);
+    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 offscreen_tab =
+      OffscreenPresentationsOwner::Get(extension_web_contents)
+          ->StartPresentation(
+              start_url,
+              (is_whitelisted_extension && params->options.presentation_id) ?
+                  *params->options.presentation_id : std::string(),
+              DetermineInitialSize(params->options));
+  if (!offscreen_tab) {
+    SetError(kTooManyOffscreenTabs);
+    return false;
+  }
+
+  if (!TabCaptureRegistry::Get(browser_context())->AddRequest(
+          offscreen_tab->web_contents(), extension()->id(), true)) {
+    // TODO(miu): Allow multiple consumers of single tab capture.
+    // http://crbug.com/535336
+    SetError(kCapturingSameOffscreenTab);
+    return false;
+  }
+  AddMediaStreamSourceConstraints(offscreen_tab->web_contents(),
+                                  &params->options);
+
+  // At this point, everything is set up in the browser process.  It's now up to
+  // the custom JS bindings in the extension's render process 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;
+}
+
+// static
+gfx::Size TabCaptureCaptureOffscreenTabFunction::DetermineInitialSize(
+    const TabCapture::CaptureOptions& options) {
+  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) {
+    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 extensions