EXO: Add support for transform to fullscreen client

Allows the fullscreen client to be executed with a custom transform.
(Valid values are 0, 90, 180, 270). This means the client will
allocate buffers in the native display space (useful for overlay
support). The transform hint is used to inform the compositor of
the correct rendering orientation of the client surface.

Bug: None
Test: wayland_fullscreen_client --transform="90"
Change-Id: I6be91c8f6d3a027466581f680c186614fcbd25d9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1631728
Commit-Queue: Daniel Nicoara <dnicoara@chromium.org>
Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Cr-Commit-Position: refs/heads/master@{#664377}

components/exo/wayland/clients/fullscreen_shell.cc

@@ -118,7 +118,8 @@ void FullscreenClient::Paint(const wl_callback_listener& frame_listener) {
 
   wl_surface_set_buffer_scale(surface_.get(), scale_);
   wl_surface_set_buffer_transform(surface_.get(), transform_);
-  wl_surface_damage(surface_.get(), 0, 0, size_.width(), size_.height());
+  wl_surface_damage(surface_.get(), 0, 0, surface_size_.width(),
+                    surface_size_.height());
   wl_surface_attach(surface_.get(), buffer->buffer.get(), 0, 0);
 
   // Set up the frame callback.
@@ -156,6 +157,19 @@ void FullscreenClient::HandleMode(void* data,
     return;
 
   size_.SetSize(width, height);
+  switch (transform_) {
+    case WL_OUTPUT_TRANSFORM_NORMAL:
+    case WL_OUTPUT_TRANSFORM_180:
+      surface_size_.SetSize(width, height);
+      break;
+    case WL_OUTPUT_TRANSFORM_90:
+    case WL_OUTPUT_TRANSFORM_270:
+      surface_size_.SetSize(height, width);
+      break;
+    default:
+      NOTREACHED();
+      break;
+  }
 
   std::unique_ptr<wl_region> opaque_region(static_cast<wl_region*>(
       wl_compositor_create_region(globals_.compositor.get())));