Copy some diagnostic values to the stack and alias them.

Temporarily add some values to minidumps, to help diagnose BlobReader
crash reports.

Bug: 864351
Change-Id: I70a8b36e83fdb1c43f698d83aaf6b712da6a9264
Reviewed-on: https://chromium-review.googlesource.com/1185906Reviewed-by: Marijn Kruisselbrink <mek@chromium.org>
Commit-Queue: Wez <wez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#585337}

storage/browser/blob/blob_reader.cc

@@ -14,6 +14,7 @@
 
 #include "base/bind.h"
 #include "base/callback_helpers.h"
+#include "base/debug/alias.h"
 #include "base/memory/ptr_util.h"
 #include "base/task/post_task.h"
 #include "base/time/time.h"
@@ -481,7 +482,21 @@ BlobReader::Status BlobReader::ReadItem() {
 
   // Do the reading.
   const BlobDataItem& item = *items.at(current_item_index_);
+
+  // TODO(https://crbug.com/864351): Temporary diagnostics.
+  uint64_t item_offset = item.offset();
+  base::debug::Alias(&item_offset);
+  uint64_t item_length = item.length();
+  base::debug::Alias(&item_length);
+  int buf_bytes_remaining = read_buf_->BytesRemaining();
+  base::debug::Alias(&buf_bytes_remaining);
+  base::debug::Alias(&bytes_to_read);
+
   if (item.type() == BlobDataItem::Type::kBytes) {
+    // TODO(https://crbug.com/864351): Temporary diagnostics.
+    const char* item_bytes = item.bytes().data();
+    base::debug::Alias(&item_bytes);
+
     ReadBytesItem(item, bytes_to_read);
     return Status::DONE;
   }

storage/browser/blob/mojo_blob_reader.cc

@@ -4,6 +4,7 @@
 
 #include "storage/browser/blob/mojo_blob_reader.h"
 
+#include "base/debug/alias.h"
 #include "base/trace_event/trace_event.h"
 #include "net/base/io_buffer.h"
 #include "services/network/public/cpp/net_adapters.h"
@@ -99,17 +100,28 @@ void MojoBlobReader::DidCalculateSize(int result) {
   TRACE_EVENT_ASYNC_END2("Blob", "BlobReader::CountSize", this, "result",
                          "success", "size", blob_reader_->total_size());
 
+  // TODO(https://crbug.com/864351): Temporary diagnostics.
+  net::HttpByteRange pre_bounds_range = byte_range_;
+  base::debug::Alias(&pre_bounds_range);
+
   // Apply the range requirement.
   if (!byte_range_.ComputeBounds(blob_reader_->total_size())) {
     NotifyCompletedAndDeleteIfNeeded(net::ERR_REQUEST_RANGE_NOT_SATISFIABLE);
     return;
   }
 
+  // TODO(https://crbug.com/864351): Temporary diagnostics.
+  net::HttpByteRange post_bounds_range = byte_range_;
+  base::debug::Alias(&post_bounds_range);
+
   DCHECK_LE(byte_range_.first_byte_position(),
             byte_range_.last_byte_position() + 1);
   uint64_t length = base::checked_cast<uint64_t>(
       byte_range_.last_byte_position() - byte_range_.first_byte_position() + 1);
 
+  // TODO(https://crbug.com/864351): Temporary diagnostics.
+  base::debug::Alias(&length);
+
   if (blob_reader_->SetReadRange(byte_range_.first_byte_position(), length) !=
       BlobReader::Status::DONE) {
     NotifyCompletedAndDeleteIfNeeded(blob_reader_->net_error());