Added .proto parsing and convertion to .fbs.

Bug: 15777858
Change-Id: Iabef9b8c8044e593bb89510feebdee00d2f1840b
Tested: on Linux and Windows.

tests/prototest/test.golden

@@ -0,0 +1,32 @@
+// Generated from test.proto
+
+namespace proto.test;
+
+enum ProtoEnum : short {
+  FOO = 1,
+  BAR = 5,
+}
+
+table OtherMessage {
+  a:double;
+  b:float = 3.14149;
+}
+
+table ProtoMessage {
+  c:int = 16;
+  d:long;
+  p:uint;
+  e:ulong;
+  f:int = -1;
+  g:long;
+  h:uint;
+  q:ulong;
+  i:int;
+  j:long;
+  k:bool;
+  l:string (required);
+  m:string;
+  n:OtherMessage;
+  o:[string];
+}
+

tests/prototest/test.proto

@@ -0,0 +1,34 @@
+// Sample .proto file that we can translate to the corresponding .fbs.
+
+package proto.test;
+
+option some_option = is_ignored;
+import "some_other_schema.proto";
+
+enum ProtoEnum {
+  FOO = 1;
+  BAR = 5;
+}
+
+message OtherMessage {
+  optional double a = 26;
+  optional float b = 32 [default = 3.14149];
+}
+
+message ProtoMessage {
+  optional int32 c = 12 [default = 16];
+  optional int64 d = 1 [default = 0];
+  optional uint32 p = 1;
+  optional uint64 e = 2;
+  optional sint32 f = 3 [default = -1];
+  optional sint64 g = 4;
+  optional fixed32 h = 5;
+  optional fixed64 q = 6;
+  optional sfixed32 i = 7;
+  optional sfixed64 j = 8;
+  optional bool k = 9;
+  required string l = 10;
+  optional bytes m = 11;
+  optional OtherMessage n = 12;
+  repeated string o = 14;
+}