Use static_cast instead of reinterpret_cast for downcasting

static_cast is better suited for downcasting since it can check that the
types are related.

/components/paint_preview
This CL was uploaded by git cl split.

R=mahmoudi@chromium.org

Change-Id: I64f78a148bd456e687c1f0948904776925d3ba3f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2435699
Auto-Submit: Kevin McNee <mcnee@chromium.org>
Reviewed-by: Mehran Mahmoudi <mahmoudi@chromium.org>
Commit-Queue: Mehran Mahmoudi <mahmoudi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#811733}

components/paint_preview/player/player_compositor_delegate_unittest.cc

@@ -155,12 +155,12 @@ class FakePaintPreviewCompositorService : public PaintPreviewCompositorService {
 
 FakePaintPreviewCompositorClient* AsFakeClient(
     PaintPreviewCompositorClient* client) {
-  return reinterpret_cast<FakePaintPreviewCompositorClient*>(client);
+  return static_cast<FakePaintPreviewCompositorClient*>(client);
 }
 
 FakePaintPreviewCompositorService* AsFakeService(
     PaintPreviewCompositorService* service) {
-  return reinterpret_cast<FakePaintPreviewCompositorService*>(service);
+  return static_cast<FakePaintPreviewCompositorService*>(service);
 }
 
 class PlayerCompositorDelegateImpl : public PlayerCompositorDelegate {