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.

/chrome/browser/paint_preview
This CL was uploaded by git cl split.

R=ckitagawa@chromium.org

Change-Id: If816d7c4d2d7d898688497b0d368d6145eeaaf68
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2435998
Auto-Submit: Kevin McNee <mcnee@chromium.org>
Reviewed-by: Calder Kitagawa <ckitagawa@chromium.org>
Commit-Queue: Calder Kitagawa <ckitagawa@chromium.org>
Cr-Commit-Position: refs/heads/master@{#811307}

chrome/browser/paint_preview/paint_preview_compositor_browsertest.cc

@@ -39,14 +39,14 @@ std::unique_ptr<PaintPreviewCompositorServiceImpl> ToCompositorServiceImpl(
     std::unique_ptr<PaintPreviewCompositorService, base::OnTaskRunnerDeleter>
         service) {
   return std::unique_ptr<PaintPreviewCompositorServiceImpl>(
-      reinterpret_cast<PaintPreviewCompositorServiceImpl*>(service.release()));
+      static_cast<PaintPreviewCompositorServiceImpl*>(service.release()));
 }
 
 std::unique_ptr<PaintPreviewCompositorClientImpl> ToCompositorClientImpl(
     std::unique_ptr<PaintPreviewCompositorClient, base::OnTaskRunnerDeleter>
         client) {
   return std::unique_ptr<PaintPreviewCompositorClientImpl>(
-      reinterpret_cast<PaintPreviewCompositorClientImpl*>(client.release()));
+      static_cast<PaintPreviewCompositorClientImpl*>(client.release()));
 }
 
 bool IsBoundAndConnected(PaintPreviewCompositorClientImpl* compositor) {