Fix error handling in POSIX version of the base::File::GetLength.

content/browser/renderer_host/media/audio_input_debug_writer_unittest.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <stdint.h>
 
 #include "base/files/file_util.h"
 #include "base/memory/ptr_util.h"
 #include "base/synchronization/waitable_event.h"
 #include "base/sys_byteorder.h"
@@ skipping 65 matching lines @@
                            int writes,
                            int64_t file_length) {
     uint32_t block_align = params.channels() * kBytesPerSample;
     uint32_t data_size =
         static_cast<uint32_t>(params.frames_per_buffer() * params.channels() *
                               writes * kBytesPerSample);
     // Offset Length  Content
     //  0      4     "RIFF"
     EXPECT_EQ(0, strncmp(wav_header, "RIFF", 4));
     //  4      4     <file length - 8>
+    ASSERT_GT(file_length, 8);
     EXPECT_EQ(static_cast<uint64_t>(file_length - 8), ReadLE4(wav_header + 4));
     EXPECT_EQ(static_cast<uint32_t>(data_size + kWavHeaderSize - 8),
               ReadLE4(wav_header + 4));
     //  8      4     "WAVE"
     // 12      4     "fmt "
     EXPECT_EQ(0, strncmp(wav_header + 8, "WAVEfmt ", 8));
     // 16      4     <length of the fmt data> (=16)
     EXPECT_EQ(16U, ReadLE4(wav_header + 16));
     // 20      2     <WAVE file encoding tag>
     EXPECT_EQ(kPcmEncoding, ReadLE2(wav_header + 20));
@@ skipping 244 matching lines @@
     AudioInputDebugWriterBehavioralTest,
     // Using 10ms frames per buffer everywhere.
     testing::Values(
         // No writes.
         std::tr1::make_tuple(media::ChannelLayout::CHANNEL_LAYOUT_MONO,
                              44100,
                              44100 / 100,
                              100)));
 
 }  // namespace content