Fix a crash when chooseDesktopMedia is called with no target tab

chrome/browser/extensions/api/desktop_capture/desktop_capture_api.cc

 // Copyright 2013 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/browser/extensions/api/desktop_capture/desktop_capture_api.h"
 
 #include "base/command_line.h"
 #include "base/compiler_specific.h"
 #include "base/strings/utf_string_conversions.h"
 #include "chrome/browser/extensions/extension_tab_util.h"
@@ skipping 19 matching lines @@
 const char kInvalidSourceNameError[] = "Invalid source type specified.";
 const char kEmptySourcesListError[] =
     "At least one source type must be specified.";
 const char kTabCaptureNotSupportedError[] = "Tab capture is not supported yet.";
 const char kNoTabIdError[] = "targetTab doesn't have id field set.";
 const char kNoUrlError[] = "targetTab doesn't have URL field set.";
 const char kInvalidTabIdError[] = "Invalid tab specified.";
 const char kTabUrlChangedError[] = "URL for the specified tab has changed.";
 const char kTabUrlNotSecure[] =
     "URL scheme for the specified tab is not secure.";
+const char kNoTabsAvailableError[] = "No tabs available.";
 
 DesktopCaptureChooseDesktopMediaFunction::PickerFactory* g_picker_factory =
     NULL;
 
 }  // namespace
 
 // static
 void DesktopCaptureChooseDesktopMediaFunction::SetPickerFactoryForTests(
     PickerFactory* factory) {
   g_picker_factory = factory;
@@ skipping 32 matching lines @@
   args_->Remove(0, NULL);
 
   scoped_ptr<api::desktop_capture::ChooseDesktopMedia::Params> params =
       api::desktop_capture::ChooseDesktopMedia::Params::Create(*args_);
   EXTENSION_FUNCTION_VALIDATE(params.get());
 
   DesktopCaptureRequestsRegistry::GetInstance()->AddRequest(
       render_view_host()->GetProcess()->GetID(), request_id_, this);
 
   gfx::NativeWindow parent_window;
-  content::RenderViewHost* render_view;
+  content::RenderViewHost* render_view = NULL;
+  content::WebContents* web_contents = NULL;
   base::string16 target_name;
   if (params->target_tab) {
     if (!params->target_tab->url) {
       error_ = kNoUrlError;
       return false;
     }
     origin_ = GURL(*(params->target_tab->url)).GetOrigin();
 
     if (!CommandLine::ForCurrentProcess()->HasSwitch(
             switches::kAllowHttpScreenCapture) &&
         !origin_.SchemeIsSecure()) {
       error_ = kTabUrlNotSecure;
       return false;
     }
     target_name = base::UTF8ToUTF16(origin_.SchemeIsSecure() ?
         net::GetHostAndOptionalPort(origin_) : origin_.spec());
 
     if (!params->target_tab->id) {
       error_ = kNoTabIdError;
       return false;
     }
 
-    content::WebContents* web_contents = NULL;
     if (!ExtensionTabUtil::GetTabById(*(params->target_tab->id), GetProfile(),
                                       true, NULL, NULL, &web_contents, NULL)) {
       error_ = kInvalidTabIdError;
       return false;
     }
 
     GURL current_origin_ =
         web_contents->GetLastCommittedURL().GetOrigin();
     if (current_origin_ != origin_) {
       error_ = kTabUrlChangedError;
       return false;
     }
 
     // Register to be notified when the tab is closed.
     Observe(web_contents);
 
     render_view = web_contents->GetRenderViewHost();
     parent_window = web_contents->GetTopLevelNativeWindow();
   } else {
     origin_ = GetExtension()->url();
     target_name = base::UTF8ToUTF16(GetExtension()->name());
     render_view = render_view_host();
-    parent_window =
-        GetAssociatedWebContents()->GetTopLevelNativeWindow();
+
+    web_contents = GetAssociatedWebContents();
+    if (!web_contents) {
+      error_ = kNoTabsAvailableError;

[zel, 2014/05/28 04:06:34]

I still think we could support this scenario as well if the UI displays system
modal dialog in the case when parent_window and web_contents are NULL. I am not
sure that we have real-life use case of that tough.

[Sergey Ulanov, 2014/06/01 01:31:38]

I agree. I think in this case we should pass null parent_web_contents to
DesktopMediaPickerDialog and then it should use
DialogDelegate::CreateDialogWidget() to create dialog instead of
WebContentsModalDialogManager to show the dialog (the way it worked before
https://codereview.chromium.org/281383008/diff/90001/chrome/browser/ui/views/...).

[tbarzic, 2014/06/03 01:18:51]

We still need to select the parent_window to use if GetAssociatedWebContents
returns NULL. Looking at the code, views seem to handle the situation where
parent_window is NULL well. I'm not sure what should be done on Mac, though

+      return false;
+    }
+
+    parent_window = web_contents->GetTopLevelNativeWindow();
   }
+
   render_process_id_ = render_view->GetProcess()->GetID();
   render_view_id_ = render_view->GetRoutingID();
 
   bool show_screens = false;
   bool show_windows = false;
 
   for (std::vector<api::desktop_capture::DesktopCaptureSourceType>::iterator
        it = params->sources.begin(); it != params->sources.end(); ++it) {
     switch (*it) {
       case api::desktop_capture::DESKTOP_CAPTURE_SOURCE_TYPE_NONE:
@@ skipping 50 matching lines @@
 #if defined(TOOLKIT_VIEWS) || defined(OS_MACOSX)
     picker_ = DesktopMediaPicker::Create();
 #else
     error_ = "Desktop Capture API is not yet implemented for this platform.";
     return false;
 #endif
   }
   DesktopMediaPicker::DoneCallback callback = base::Bind(
       &DesktopCaptureChooseDesktopMediaFunction::OnPickerDialogResults, this);
 
-  picker_->Show(web_contents(),
+  picker_->Show(web_contents,
                 parent_window, parent_window,
                 base::UTF8ToUTF16(GetExtension()->name()),
                 target_name,
                 media_list.Pass(), callback);
   return true;
 }
 
 void DesktopCaptureChooseDesktopMediaFunction::WebContentsDestroyed() {
   Cancel();
 }
@@ skipping 70 matching lines @@
 
 void DesktopCaptureRequestsRegistry::CancelRequest(int process_id,
                                                    int request_id) {
   RequestsMap::iterator it = requests_.find(RequestId(process_id, request_id));
   if (it != requests_.end())
     it->second->Cancel();
 }
 
 
 }  // namespace extensions