Fix dragging supported files to tab strip.

chrome/browser/ui/views/tabs/tab_strip.cc

Index: chrome/browser/ui/views/tabs/tab_strip.cc
diff --git a/chrome/browser/ui/views/tabs/tab_strip.cc b/chrome/browser/ui/views/tabs/tab_strip.cc
index 8a63d2bf7cb711bac84d85a4fb450ba93f695c90..bd9c4a689165e5fc987cfbc5839ea7493b5d092d 100644
--- a/chrome/browser/ui/views/tabs/tab_strip.cc
+++ b/chrome/browser/ui/views/tabs/tab_strip.cc
@@ -17,7 +17,9 @@
 #include "base/metrics/histogram.h"
 #include "base/stl_util.h"
 #include "base/strings/utf_string_conversions.h"
+#include "base/task_runner_util.h"
 #include "chrome/browser/defaults.h"
+#include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/ui/host_desktop.h"
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
 #include "chrome/browser/ui/view_ids.h"
@@ -27,9 +29,14 @@
 #include "chrome/browser/ui/views/tabs/tab_strip_controller.h"
 #include "chrome/browser/ui/views/tabs/tab_strip_observer.h"
 #include "chrome/browser/ui/views/touch_uma/touch_uma.h"
+#include "content/public/browser/browser_thread.h"
+#include "content/public/browser/plugin_service.h"
 #include "content/public/browser/user_metrics.h"
+#include "content/public/common/webplugininfo.h"
 #include "grit/generated_resources.h"
 #include "grit/theme_resources.h"
+#include "ipc/ipc_message.h"
+#include "net/base/net_util.h"
 #include "ui/base/accessibility/accessible_view_state.h"
 #include "ui/base/default_theme_provider.h"
 #include "ui/base/dragdrop/drag_drop_types.h"
@@ -290,6 +297,20 @@ TabDragController::EventSource EventSourceFromEvent(
       TabDragController::EVENT_SOURCE_MOUSE;
 }
 
+// Get the MIME type of the file pointed to by the url. This must be called
+// from an thread that allows IO.
+std::string FindURLMimeType(GURL url) {
+  base::FilePath full_path;
+  net::FileURLToFilePath(url, &full_path);
+
+  std::string mime_type;
+  // Get the MIME type based on the file path's extension.
+  // This may use registry or file IO.
+  net::GetMimeTypeFromFile(full_path, &mime_type);
+
+  return mime_type;
+}
+
 }  // namespace
 
 ///////////////////////////////////////////////////////////////////////////////
@@ -609,13 +630,15 @@ TabStrip::TabStrip(TabStripController* controller)
       current_selected_width_(Tab::GetStandardSize().width()),
       available_width_for_tabs_(-1),
       in_tab_close_(false),
+      drag_file_supported_(true),
       animation_container_(new gfx::AnimationContainer()),
       bounds_animator_(this),
       layout_type_(TAB_STRIP_LAYOUT_SHRINK),
       adjust_layout_(false),
       reset_to_shrink_on_exit_(false),
       mouse_move_count_(0),
-      immersive_style_(false) {
+      immersive_style_(false),
+      weak_ptr_factory_(this) {
   Init();
 }
 
@@ -1395,6 +1418,27 @@ gfx::Size TabStrip::GetPreferredSize() {
 }
 
 void TabStrip::OnDragEntered(const DropTargetEvent& event) {
+  // Clear information about previous drag operation.
+  drag_url_ = GURL();
+  drag_file_supported_ = true;
+
+  GURL url;
+  string16 title;
+  if (event.data().GetURLAndTitle(&url, &title) && url.is_valid()) {

[asanka, 2013/11/15 19:15:22]

The logic below here only applies to file:// URLs. For other schemes, we'll have
to assume that the URL is supported since the MIME type won't be known until the
request has been issued.

[sky, 2013/11/15 20:46:37]

None-the-less there is no point doing the same test as is done @ 1473. 

[asanka, 2013/11/15 21:01:13]

Yup.

[michaelpg, 2013/11/15 21:08:01]

The check here esnures we don't request unnecessary IO. asanka@ is right that I
should add the condition url.SchemaIsFile() to this if statement.

drop_data_supported_ defaults to true, so for non-file-schema URLs, the check at
1473 will still be necessary.... unless I set drag_file_supported to false in an
else statement here, regardless of the schema. Which makes sense now that I
think about it.

+    // Cache the URL associated with the current drag.
+    drag_url_ = url;
+
+    // Get the MIME type of the file based on the file path's extension.
+    // Pass the input URL to be certain which URL the reply is for.
+    base::PostTaskAndReplyWithResult(
+        content::BrowserThread::GetBlockingPool(),
+        FROM_HERE,
+        base::Bind(&FindURLMimeType, url),
+        base::Bind(&TabStrip::OnFindURLMimeTypeCompleted,
+                   weak_ptr_factory_.GetWeakPtr(),
+                   url));
+  }
+
   // Force animations to stop, otherwise it makes the index calculation tricky.
   StopAnimating(true);
 
@@ -1403,6 +1447,10 @@ void TabStrip::OnDragEntered(const DropTargetEvent& event) {
 
 int TabStrip::OnDragUpdated(const DropTargetEvent& event) {
   UpdateDropIndex(event);
+
+  if (!drag_file_supported_)
+    return ui::DragDropTypes::DRAG_NONE;
+
   return GetDropEffect(event);
 }
 
@@ -1422,7 +1470,8 @@ int TabStrip::OnPerformDrop(const DropTargetEvent& event) {
 
   GURL url;
   string16 title;
-  if (!event.data().GetURLAndTitle(&url, &title) || !url.is_valid())
+  if (!drag_file_supported_ || !event.data().GetURLAndTitle(&url, &title) ||

[sky, 2013/11/15 00:48:54]

We shouldn't need to check url/title twice.

[michaelpg, 2013/11/18 23:24:51]

Done, as per above.

+      !url.is_valid())
     return ui::DragDropTypes::DRAG_NONE;
 
   controller()->PerformDrop(drop_before, drop_index, url);
@@ -2040,6 +2089,27 @@ void TabStrip::StoppedDraggingTab(Tab* tab, bool* is_first_tab) {
       tab, new ResetDraggingStateDelegate(tab), true);
 }
 
+void TabStrip::OnFindURLMimeTypeCompleted(GURL url,
+                                          const std::string& mime_type) {
+  // If this is a reply for the current URL, check if the file is unsupported.
+  // If the MIME type is empty, we do not have enough info to disallow the drag.
+  if (url == drag_url_ && !mime_type.empty() &&
+      !net::IsSupportedMimeType(mime_type)) {
+    // Check whether there is a plugin that supports the mime type (e.g. PDF).
+    // TODO(bauerb): This possibly uses stale information, but it's guaranteed
+    // not to do disk access.
+    bool allow_wildcard = false;
+    content::WebPluginInfo plugin;
+    if (!content::PluginService::GetInstance()->GetPluginInfo(
+            -1,                // process ID
+            MSG_ROUTING_NONE,  // routing ID
+            controller()->GetProfile()->GetResourceContext(),
+            url, GURL(), mime_type, allow_wildcard,
+            NULL, &plugin, NULL))
+      drag_file_supported_ = false;
+  }
+}
+
 void TabStrip::OwnDragController(TabDragController* controller) {
   // Typically, ReleaseDragController() and OwnDragController() calls are paired
   // via corresponding calls to TabDragController::Detach() and