Ozone/DRM: Alternative fix for cursor stopping on Chrome OS

We would like the bitmap list in BitmapCursorOzone to be either empty
or every bitmap be valid. If the provided bitmap is null, just don't
add it to the list. Instances created from WebCursors can sometimes
have null bitmaps.

Bug: 620927
Change-Id: I0e78bfcb544fe6751dc48e378e495feaec220af8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1789909Reviewed-by: Robert Kroeger <rjkroege@chromium.org>
Commit-Queue: Saman Sami <samans@chromium.org>
Cr-Commit-Position: refs/heads/master@{#694320}

ui/base/cursor/ozone/bitmap_cursor_factory_ozone.cc

@@ -38,7 +38,8 @@ scoped_refptr<BitmapCursorOzone> CreateDefaultBitmapCursor(CursorType type) {
 BitmapCursorOzone::BitmapCursorOzone(const SkBitmap& bitmap,
                                      const gfx::Point& hotspot)
     : hotspot_(hotspot), frame_delay_ms_(0) {
-  bitmaps_.push_back(bitmap);
+  if (!bitmap.isNull())
+    bitmaps_.push_back(bitmap);
 }
 
 BitmapCursorOzone::BitmapCursorOzone(const std::vector<SkBitmap>& bitmaps,
@@ -47,6 +48,11 @@ BitmapCursorOzone::BitmapCursorOzone(const std::vector<SkBitmap>& bitmaps,
     : bitmaps_(bitmaps), hotspot_(hotspot), frame_delay_ms_(frame_delay_ms) {
   DCHECK_LT(0U, bitmaps.size());
   DCHECK_LE(0, frame_delay_ms);
+  // No null bitmap should be in the list. Blank cursors should just be an empty
+  // vector.
+  DCHECK(std::find_if(bitmaps_.begin(), bitmaps_.end(),
+                      [](const SkBitmap& bitmap) { return bitmap.isNull(); }) ==
+         bitmaps_.end());
 }
 
 BitmapCursorOzone::~BitmapCursorOzone() {