Expose thumbnails of pages to iOS share extensions.

ios/chrome/browser/ui/ui_util.h

Index: ios/chrome/browser/ui/ui_util.h
diff --git a/ios/chrome/browser/ui/ui_util.h b/ios/chrome/browser/ui/ui_util.h
index 1bef1f04e1b41d1bf6a5af1f91642d6d3624b556..9518febb02a6dfd161d5b4722c6f55791b6c9f28 100644
--- a/ios/chrome/browser/ui/ui_util.h
+++ b/ios/chrome/browser/ui/ui_util.h
@@ -74,13 +74,18 @@ enum class ProjectionMode {
   // |projectTo| and |revisedTargetSize| will be set to |targetSize|
   kFill,
 
-  // Scale to the target, maintaining aspect ratio, clipping the excess. Large
-  // original sizes are shrunk until they fit on one side, small original sizes
-  // are expanded.
+  // Scale to the target, maintaining aspect ratio, clipping the excess, while
+  // keeping the image centered.
+  // Large original sizes are shrunk until they fit on one side, small original
+  // sizes are expanded.
   // |projectTo| will be a subset of |originalSize|
   // |revisedTargetSize| will be set to |targetSize|
   kAspectFill,
 
+  // Same as kAspectFill, except that the bottom part of the image will be
+  // clipped. The image will still be horizontally centered.
+  kAspectFillAlignTop,
+
   // Fit the image in the target so it fits completely inside, preserving aspect
   // ratio. This will leave bands with with no data in the target.
   // |projectTo| will be set to |originalSize|