vaapi: extract vaCreateContext() to its own method in VaapiWrapper

This CL extracts the call to vaCreateContext() out of VaapiWrapper's
CreateSurfaces() and into a new method VaapiWrapper::CreateContext().

The former still calls the latter, but this change allows for separating
the allocation of the surfaces from the creation of the context. In
particular, this is needed for decoding directly on client Surfaces
(see the bug and/or the experimental CL crrev.com/c/986353. from
which this code is separated).

Bug: 822346
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel
Change-Id: I37f28d2a0fe939264d3153f34bd25bbc6c77ba79
Reviewed-on: https://chromium-review.googlesource.com/995623Reviewed-by: Kristian H. Kristensen <hoegsberg@chromium.org>
Commit-Queue: Miguel Casas <mcasas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#548515}

media/gpu/vaapi/vaapi_wrapper.cc

@@ -746,19 +746,25 @@ bool VaapiWrapper::CreateSurfaces(unsigned int va_format,
   }
 
   // And create a context associated with them.
-  va_res = vaCreateContext(va_display_, va_config_id_, size.width(),
-                           size.height(), VA_PROGRESSIVE, &va_surface_ids_[0],
-                           va_surface_ids_.size(), &va_context_id_);
-
-  VA_LOG_ON_ERROR(va_res, "vaCreateContext failed");
-  if (va_res != VA_STATUS_SUCCESS) {
+  const bool success = CreateContext(va_format, size, va_surface_ids_);
+  if (success)
+    *va_surfaces = va_surface_ids_;
+  else
     DestroySurfaces_Locked();
-    return false;
-  }
+  return success;
+}
 
-  *va_surfaces = va_surface_ids_;
-  va_surface_format_ = va_format;
-  return true;
+bool VaapiWrapper::CreateContext(unsigned int va_format,
+                                 const gfx::Size& size,
+                                 const std::vector<VASurfaceID>& va_surfaces) {
+  VAStatus va_res = vaCreateContext(
+      va_display_, va_config_id_, size.width(), size.height(), VA_PROGRESSIVE,
+      &va_surface_ids_[0], va_surface_ids_.size(), &va_context_id_);
+
+  VA_LOG_ON_ERROR(va_res, "vaCreateContext failed");
+  if (va_res == VA_STATUS_SUCCESS)
+    va_surface_format_ = va_format;
+  return va_res == VA_STATUS_SUCCESS;
 }
 
 void VaapiWrapper::DestroySurfaces() {

media/gpu/vaapi/vaapi_wrapper.h

@@ -89,7 +89,7 @@ class MEDIA_GPU_EXPORT VaapiWrapper
   // Return true when JPEG encode is supported.
   static bool IsJpegEncodeSupported();
 
-  // Create |num_surfaces| backing surfaces in driver for VASurfaces of
+  // Creates |num_surfaces| backing surfaces in driver for VASurfaces of
   // |va_format|, each of size |size|. Returns true when successful, with the
   // created IDs in |va_surfaces| to be managed and later wrapped in
   // VASurfaces.
@@ -102,7 +102,12 @@ class MEDIA_GPU_EXPORT VaapiWrapper
                               size_t num_surfaces,
                               std::vector<VASurfaceID>* va_surfaces);
 
-  // Free all memory allocated in CreateSurfaces.
+  // Creates a VA Context associated with the set of |va_surfaces| of |size|.
+  bool CreateContext(unsigned int va_format,
+                     const gfx::Size& size,
+                     const std::vector<VASurfaceID>& va_surfaces);
+
+  // Frees all memory allocated in CreateSurfaces.
   virtual void DestroySurfaces();
 
   // Create a VASurface for |pixmap|. The ownership of the surface is