Add ClientConfig proto, and JSON generation/parsing.

components/data_reduction_proxy/core/common/BUILD.gn

Index: components/data_reduction_proxy/core/common/BUILD.gn
diff --git a/components/data_reduction_proxy/core/common/BUILD.gn b/components/data_reduction_proxy/core/common/BUILD.gn
index a28e6d0216be9dc1e4d08a087d8850978c86fe0b..e659cd4296f73032aeb6f975ab1e27fb67594ef6 100644
--- a/components/data_reduction_proxy/core/common/BUILD.gn
+++ b/components/data_reduction_proxy/core/common/BUILD.gn
@@ -6,6 +6,8 @@ import("//chrome/version.gni")
 
 static_library("common") {
   sources = [
+    "client_config_parser.cc",
+    "client_config_parser.h",
     "data_reduction_proxy_bypass_type_list.h",
     "data_reduction_proxy_config_values.h",
     "data_reduction_proxy_event_store.cc",
@@ -25,6 +27,7 @@ static_library("common") {
   ]
   deps = [
     "//base",
+    "//components/data_reduction_proxy/proto:data_reduction_proxy_proto",
     "//net",
     "//url",
   ]
@@ -54,6 +57,7 @@ source_set("test_support") {
 source_set("unit_tests") {
   testonly = true
   sources = [
+    "client_config_parser_unittest.cc",
     "data_reduction_proxy_event_store_unittest.cc",
     "data_reduction_proxy_headers_unittest.cc",
     "data_reduction_proxy_params_unittest.cc",
@@ -64,6 +68,7 @@ source_set("unit_tests") {
     ":test_support",
     "//base",
     "//base/test:test_support",
+    "//components/data_reduction_proxy/proto:data_reduction_proxy_proto",
     "//net:test_support",
     "//testing/gtest",
   ]