[XProto] Fix crash when using VNC session

When running under a VNC session, the connection setup data sometimes
has duplicated depths, like so:

depth=24: visuals={123,456}
depth=24: visuals={789}

Previously, we were searching for the unique depth that matches the
root depth, then searching for the visual within the list
corresponding to that depth.  However, since the depths may not be
unique, search through all depths until we find a matching visual ID,
and then use that to set both the default depth and default visual.

R=sky

Change-Id: I51f75260f584f85f2bdc93048e6c4848cf00997a
Fixes: 1121438, 1115929
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2375888Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
Auto-Submit: Thomas Anderson <thomasanderson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#802371}

ui/gfx/x/connection.cc

@@ -238,16 +238,7 @@ Connection::Connection(const std::string& address)
         xcb_get_setup(XcbConnection())));
     setup_ = Read<Setup>(&buf);
     default_screen_ = &setup_.roots[DefaultScreenId()];
-    default_root_depth_ = &*std::find_if(
-        default_screen_->allowed_depths.begin(),
-        default_screen_->allowed_depths.end(), [&](const Depth& depth) {
-          return depth.depth == default_screen_->root_depth;
-        });
-    default_root_visual_ = &*std::find_if(
-        default_root_depth_->visuals.begin(),
-        default_root_depth_->visuals.end(), [&](const VisualType visual) {
-          return visual.visual_id == default_screen_->root_visual;
-        });
+    InitRootDepthAndVisual();
   } else {
     // Default-initialize the setup data so we always have something to return.
     setup_.roots.emplace_back();
@@ -470,6 +461,19 @@ void Connection::Dispatch(Delegate* delegate) {
   }
 }
 
+void Connection::InitRootDepthAndVisual() {
+  for (auto& depth : default_screen_->allowed_depths) {
+    for (auto& visual : depth.visuals) {
+      if (visual.visual_id == default_screen_->root_visual) {
+        default_root_depth_ = &depth;
+        default_root_visual_ = &visual;
+        return;
+      }
+    }
+  }
+  NOTREACHED();
+}
+
 void Connection::AddRequest(unsigned int sequence,
                             FutureBase::ResponseCallback callback) {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);

ui/gfx/x/connection.h

@@ -149,6 +149,8 @@ class COMPONENT_EXPORT(X11) Connection : public XProto,
     FutureBase::ResponseCallback callback;
   };
 
+  void InitRootDepthAndVisual();
+
   void AddRequest(unsigned int sequence, FutureBase::ResponseCallback callback);
 
   bool HasNextResponse() const;