Add some out-parameter initialization and DCHECKs in Mojo call-sites.

Cq-Include-Trybots: luci.chromium.try:linux_mojo
Change-Id: Ib3e4cfd6eac23f6950831751d5f079f48738c4c7
Reviewed-on: https://chromium-review.googlesource.com/1176553Reviewed-by: Ken Rockot <rockot@chromium.org>
Reviewed-by: Daniel Murphy <dmurph@chromium.org>
Commit-Queue: Wez <wez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#584792}

mojo/public/cpp/system/handle.h

@@ -125,7 +125,7 @@ class ScopedHandleBase {
 
   bool is_valid() const { return handle_.is_valid(); }
 
-  explicit operator bool() const { return handle_; }
+  explicit operator bool() const { return handle_.is_valid(); }
 
   bool operator==(const ScopedHandleBase& other) const {
     return handle_.value() == other.get().value();

services/network/public/cpp/net_adapters.cc

@@ -26,7 +26,7 @@ MojoResult NetToMojoPendingBuffer::BeginWrite(
     mojo::ScopedDataPipeProducerHandle* handle,
     scoped_refptr<NetToMojoPendingBuffer>* pending,
     uint32_t* num_bytes) {
-  void* buf;
+  void* buf = nullptr;
   *num_bytes = 0;
   MojoResult result =
       (*handle)->BeginWriteData(&buf, num_bytes, MOJO_WRITE_DATA_FLAG_NONE);
@@ -41,7 +41,7 @@ MojoResult NetToMojoPendingBuffer::BeginWrite(
 mojo::ScopedDataPipeProducerHandle NetToMojoPendingBuffer::Complete(
     uint32_t num_bytes) {
   handle_->EndWriteData(num_bytes);
-  buffer_ = NULL;
+  buffer_ = nullptr;
   return std::move(handle_);
 }
 
@@ -64,7 +64,7 @@ MojoResult MojoToNetPendingBuffer::BeginRead(
     mojo::ScopedDataPipeConsumerHandle* handle,
     scoped_refptr<MojoToNetPendingBuffer>* pending,
     uint32_t* num_bytes) {
-  const void* buffer = NULL;
+  const void* buffer = nullptr;
   *num_bytes = 0;
   MojoResult result =
       (*handle)->BeginReadData(&buffer, num_bytes, MOJO_READ_DATA_FLAG_NONE);
@@ -75,7 +75,7 @@ MojoResult MojoToNetPendingBuffer::BeginRead(
 
 void MojoToNetPendingBuffer::CompleteRead(uint32_t num_bytes) {
   handle_->EndReadData(num_bytes);
-  buffer_ = NULL;
+  buffer_ = nullptr;
 }
 
 mojo::ScopedDataPipeConsumerHandle MojoToNetPendingBuffer::ReleaseHandle() {

storage/browser/blob/mojo_blob_reader.cc

@@ -145,6 +145,7 @@ void MojoBlobReader::DidReadSideData(BlobReader::Status status) {
 
 void MojoBlobReader::StartReading() {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
+  DCHECK(!response_body_stream_);
 
   response_body_stream_ = delegate_->PassDataPipe();
   peer_closed_handle_watcher_.Watch(
@@ -165,8 +166,9 @@ void MojoBlobReader::StartReading() {
 void MojoBlobReader::ReadMore() {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   DCHECK(!pending_write_.get());
+  DCHECK(response_body_stream_);
 
-  uint32_t num_bytes;
+  uint32_t num_bytes = 0;
   // TODO: we should use the abstractions in MojoAsyncResourceHandler.
   MojoResult result = network::NetToMojoPendingBuffer::BeginWrite(
       &response_body_stream_, &pending_write_, &num_bytes);
@@ -184,9 +186,10 @@ void MojoBlobReader::ReadMore() {
 
   TRACE_EVENT_ASYNC_BEGIN0("Blob", "BlobReader::ReadMore", this);
   CHECK_GT(static_cast<uint32_t>(std::numeric_limits<int>::max()), num_bytes);
+  DCHECK(pending_write_);
   auto buf =
       base::MakeRefCounted<network::NetToMojoIOBuffer>(pending_write_.get());
-  int bytes_read;
+  int bytes_read = 0;
   BlobReader::Status read_status = blob_reader_->Read(
       buf.get(), static_cast<int>(num_bytes), &bytes_read,
       base::BindOnce(&MojoBlobReader::DidRead, base::Unretained(this), false));