Tracing V2: Field number constants for protobuf plugin.

components/tracing/tools/proto_zero_plugin/proto_zero_generator.cc

Index: components/tracing/tools/proto_zero_plugin/proto_zero_generator.cc
diff --git a/components/tracing/tools/proto_zero_plugin/proto_zero_generator.cc b/components/tracing/tools/proto_zero_plugin/proto_zero_generator.cc
index 2165673b362eeefc3bbb110ca2e0be0fa6aac01c..e15dd8d6f7e1d5f7f02191bc42dd18b8a2af753d 100644
--- a/components/tracing/tools/proto_zero_plugin/proto_zero_generator.cc
+++ b/components/tracing/tools/proto_zero_plugin/proto_zero_generator.cc
@@ -93,6 +93,14 @@ class GeneratorJob {
     return name;
   }
 
+  template <class T>
+  inline std::string GetCamelCaseName(const T* descriptor, bool capitalize) {

[Primiano Tucci (use gerrit), 2016/08/05 11:34:18]

looks like capitalize is always = true.
Unless you plan to use this argument in next CLs please drop it.

+    std::string camel_name = descriptor->camelcase_name();
+    if (capitalize && !camel_name.empty())
+      camel_name.at(0) = toupper(camel_name.at(0));
+    return camel_name;
+  }
+
   // Small enums can be written faster without involving VarInt encoder.
   inline bool IsTinyEnumField(const FieldDescriptor* field) {
     if (field->type() != FieldDescriptor::TYPE_ENUM)
@@ -463,7 +471,29 @@ class GeneratorJob {
       }
     }
 
-    // Fields descriptors.
+    // Field numbers.
+    if (message->field_count() > 0) {
+      stub_h_->Print("enum : int32_t {\n");
+      stub_h_->Indent();
+
+      for (int i = 0; i < message->field_count(); ++i) {
+        const FieldDescriptor* field = message->field(i);
+        std::string name = GetCamelCaseName(field, true);
+        if (name.empty()) {
+          // Protoc allows fields like: 'bool _ = 1'.
+          Abort("Empty field name in camel case notation.");

[Primiano Tucci (use gerrit), 2016/08/05 11:34:18]

lol, TIL

+        }
+
+        stub_h_->Print(
+            "k$name$FieldNumber = $id$,\n",
+            "name", name,
+            "id", std::to_string(field->number()));
+      }
+      stub_h_->Outdent();
+      stub_h_->Print("};\n");
+    }
+
+    // Field descriptors.
     for (int i = 0; i < message->field_count(); ++i) {
       const FieldDescriptor* field = message->field(i);
       if (field->is_packed()) {