media/gpu/test/EncodedDataHelper: Fix a crash bug in reading IvfFrameHeader

This fixes a bug of EncodedDataHelper in reading ivf frame
header.

Bug: 1098142
Test: video.DecodeAccelSanity.vp9_1
Change-Id: Icaa6d6a41784bbc1b3bc1f7d967a35abb5635743
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2262022
Commit-Queue: Hirokazu Honda <hiroh@chromium.org>
Commit-Queue: David Staessens <dstaessens@chromium.org>
Auto-Submit: Hirokazu Honda <hiroh@chromium.org>
Reviewed-by: David Staessens <dstaessens@chromium.org>
Cr-Commit-Position: refs/heads/master@{#781700}

media/gpu/test/video_test_helpers.cc

@@ -268,7 +268,7 @@ base::Optional<IvfFrameHeader> EncodedDataHelper::GetNextIvfFrameHeader()
     return base::nullopt;
   }
   return GetIvfFrameHeader(base::span<const uint8_t>(
-      reinterpret_cast<const uint8_t*>(data_[pos]), kIvfFrameHeaderSize));
+      reinterpret_cast<const uint8_t*>(&data_[pos]), kIvfFrameHeaderSize));
 }
 
 base::Optional<IvfFrame> EncodedDataHelper::ReadNextIvfFrame() {