Add LOG for when IOSurface allocation fails

ui/gfx/mac/io_surface.cc

Index: ui/gfx/mac/io_surface.cc
diff --git a/ui/gfx/mac/io_surface.cc b/ui/gfx/mac/io_surface.cc
index 4441138e4d8985b7c4bfd4e5ec0ca353f6239745..b10780249f693fcc976f75673616e67bf2cdf7e8 100644
--- a/ui/gfx/mac/io_surface.cc
+++ b/ui/gfx/mac/io_surface.cc
@@ -164,6 +164,11 @@ IOSurfaceRef CreateIOSurface(const gfx::Size& size, gfx::BufferFormat format) {
   }
 
   IOSurfaceRef surface = IOSurfaceCreate(properties);
+  if (!surface) {
+    LOG(ERROR) << "Failed to allocate IOSurface of size " << size.ToString()
+               << ".";
+    return nullptr;
+  }
 
   // For unknown reasons, triggering this lock on OS X 10.9, on certain GPUs,
   // causes PDFs to render incorrectly. Hopefully this check can be removed once