mojo: Mark DataView readers as WARN_UNUSED_RESULT.

It's important to check this return value to make sure that
deserialization actually succeeded.

BUG=652129

Review-Url: https://codereview.chromium.org/2392713002
Cr-Commit-Position: refs/heads/master@{#422681}

components/arc/bluetooth/bluetooth_struct_traits.cc

@@ -34,6 +34,8 @@ namespace mojo {
 std::vector<uint8_t>
 StructTraits<arc::mojom::BluetoothUUIDDataView, device::BluetoothUUID>::uuid(
     const device::BluetoothUUID& input) {
+  // TODO(dcheng): Figure out what to do here, this is called twice on
+  // serialization. Building a vector is a little inefficient.
   std::string uuid_str = StripNonHex(input.canonical_value());
 
   std::vector<uint8_t> address_bytes;
@@ -47,7 +49,8 @@ bool StructTraits<arc::mojom::BluetoothUUIDDataView,
     arc::mojom::BluetoothUUIDDataView data,
     device::BluetoothUUID* output) {
   std::vector<uint8_t> address_bytes;
-  data.ReadUuid(&address_bytes);
+  if (!data.ReadUuid(&address_bytes))
+    return false;
 
   if (address_bytes.size() != kUUIDSize)
     return false;

mojo/public/tools/bindings/generators/cpp_templates/module-shared.h.tmpl

@@ -42,6 +42,7 @@ namespace {{namespace}} {
 #include <type_traits>
 #include <utility>
 
+#include "base/compiler_specific.h"
 #include "mojo/public/cpp/bindings/array_data_view.h"
 #include "mojo/public/cpp/bindings/enum_traits.h"
 #include "mojo/public/cpp/bindings/interface_data_view.h"

mojo/public/tools/bindings/generators/cpp_templates/struct_data_view_declaration.tmpl

@@ -21,12 +21,12 @@ class {{struct.name}}DataView {
       {{kind|cpp_data_view_type}}* output);
 
   template <typename UserType>
-  bool Read{{name|under_to_camel}}(UserType* output) {
+  WARN_UNUSED_RESULT bool Read{{name|under_to_camel}}(UserType* output) {
 {%-     if pf.min_version != 0 %}
-    auto pointer = data_->header_.version >= {{pf.min_version}}
-                   ? &data_->{{name}} : nullptr;
+    auto* pointer = data_->header_.version >= {{pf.min_version}}
+                    ? &data_->{{name}} : nullptr;
 {%-     else %}
-    auto pointer = &data_->{{name}};
+    auto* pointer = &data_->{{name}};
 {%-     endif %}
     return mojo::internal::Deserialize<{{kind|unmapped_type_for_serializer}}>(
         pointer, output, context_);
@@ -37,12 +37,12 @@ class {{struct.name}}DataView {
       {{kind|cpp_data_view_type}}* output);
 
   template <typename UserType>
-  bool Read{{name|under_to_camel}}(UserType* output) {
+  WARN_UNUSED_RESULT bool Read{{name|under_to_camel}}(UserType* output) {
 {%-     if pf.min_version != 0 %}
-    auto pointer = data_->header_.version >= {{pf.min_version}}
-                   ? data_->{{name}}.Get() : nullptr;
+    auto* pointer = data_->header_.version >= {{pf.min_version}}
+                    ? data_->{{name}}.Get() : nullptr;
 {%-     else %}
-    auto pointer = data_->{{name}}.Get();
+    auto* pointer = data_->{{name}}.Get();
 {%-     endif %}
     return mojo::internal::Deserialize<{{kind|unmapped_type_for_serializer}}>(
         pointer, output, context_);
@@ -50,7 +50,7 @@ class {{struct.name}}DataView {
 
 {%-   elif kind|is_enum_kind %}
   template <typename UserType>
-  bool Read{{name|under_to_camel}}(UserType* output) const {
+  WARN_UNUSED_RESULT bool Read{{name|under_to_camel}}(UserType* output) const {
 {%-     if pf.min_version != 0 %}
     auto data_value = data_->header_.version >= {{pf.min_version}}
                       ? data_->{{name}} : 0;

mojo/public/tools/bindings/generators/cpp_templates/union_data_view_declaration.tmpl

@@ -31,7 +31,7 @@ class {{union.name}}DataView {
       {{kind|cpp_data_view_type}}* output);
 
   template <typename UserType>
-  bool Read{{name|under_to_camel}}(UserType* output) {
+  WARN_UNUSED_RESULT bool Read{{name|under_to_camel}}(UserType* output) {
     DCHECK(is_{{name}}());
     return mojo::internal::Deserialize<{{kind|unmapped_type_for_serializer}}>(
         data_->data.f_{{name}}.Get(), output, context_);
@@ -39,7 +39,7 @@ class {{union.name}}DataView {
 
 {%-   elif kind|is_enum_kind %}
   template <typename UserType>
-  bool Read{{name|under_to_camel}}(UserType* output) const {
+  WARN_UNUSED_RESULT bool Read{{name|under_to_camel}}(UserType* output) const {
     DCHECK(is_{{name}}());
     return mojo::internal::Deserialize<{{kind|unmapped_type_for_serializer}}>(
         data_->data.f_{{name}}, output);