Modify template to sort list of source files alphabetically.

This is another step on the way to
https://fuchsia-review.googlesource.com/#/c/33945/.

I want to make it clear which source files have been
added or deleted to the automatically generated
BUILD.gn file in my manual edit. In this CL I modify the
template in order to make cosmetic-only changes to BUILD.gn.
That way in the following CL it will be easier to see the
substantive changes.
(1) Sort the list of source files in each source_set
(2) Delete some unneeded source_sets.
(3) Delete some Chromium-specific configs.

Change-Id: Id48ef59b327a1b777646f499d8030f7980c92147

templates/BUILD.gn.template

@@ -1,10 +1,14 @@
 %YAML 1.2
 --- |
-  # GRPC Chromium BUILD.gn file.
-  # This file has been automatically generated from a template file.
-  # Please look at the templates directory instead.
-  # This file can be regenerated from the template by running
-  # tools/buildgen/generate_projects.sh
+  # Copyright 2017 The Fuchsia Authors. All rights reserved.
+  # Use of this source code is governed by a BSD-style license that can be
+  # found in the LICENSE file.
+
+  # This file was created in two steps:
+  # First we ran tools/buildgen/generate_projects.sh which generates a BUILD.gn
+  # file based on the template in templates/BUILD.gn.template. Then we
+  # hand-edited the resulting file for Fuchsia.
+
   config("grpc_config") {
     include_dirs = [
       ".",
@@ -12,12 +16,6 @@
     ]
     defines = [
       "GRPC_USE_PROTO_LITE",
-      # TODO(xyzzyz): the <condition_variable> header in libstdc++-4.6 we're using
-      # in Chromium has a bug, which causes a compilation error on Clang.
-      # Therefore, we need to make gRPC not use standard library threading
-      # support.
-      # https://crbug.com/593874
-      "GRPC_CXX0X_NO_THREAD",
     ]
   }
   <%!
@@ -30,7 +28,7 @@
     if target_dict.get("build", None) == "protoc":
       deps.append("//third_party/protobuf:protoc_lib")
     name = target_dict.get("name", None)
-    if name in ("grpc++_unsecure", "grpc++", "grpc++_codegen_lib"):
+    if name in ("grpc++", "grpc++_codegen_lib"):
       deps.append("//third_party/protobuf:protobuf_lite")
     elif name in ("grpc", "grpc_unsecure"):
       deps.append("//third_party/zlib")
@@ -58,8 +56,7 @@
       or f.endswith("load_balancer_api.h")
       or f.endswith("load_balancer_api.c"))
   def wanted_lib(lib):
-    wanted_libs = ("gpr", "grpc", "grpc_unsecure", "grpc++", "grpc++_unsecure",
-                   "grpc_cronet", "grpc_plugin_support")
+    wanted_libs = ("gpr", "grpc", "grpc++", "grpc_plugin_support")
     return lib.build in ("all", "protoc") and lib.get("name", "") in wanted_libs
   def wanted_binary(tgt):
     wanted_binaries = ("grpc_cpp_plugin",)
@@ -93,19 +90,16 @@
   % endfor
   <%def name="cc_library(lib)">
   <%
-    lib_hdrs = lib.get("headers", [])
-    hdrs = [h for h in lib_hdrs if not uses_nanopb_or_protofull(h)]
-    srcs = [s for s in lib.src if not uses_nanopb_or_protofull(s)]
+    lib_hdrs = [h for h in lib.get("headers", [])
+        if not uses_nanopb_or_protofull(h)]
+    lib_srcs = [s for s in lib.src if not uses_nanopb_or_protofull(s)]
+    lib_pub =  lib.get("public_headers", [])
+    sources = lib_pub + lib_hdrs + lib_srcs
+    sources.sort()
   %>
   source_set("${lib.name}") {
     sources = [
-  % for hdr in lib.get("public_headers", []):
-      "${hdr}",
-  % endfor
-  % for hdr in hdrs:
-      "${hdr}",
-  % endfor
-  % for src in srcs:
+  % for src in sources:
       "${src}",
   % endfor
     ]
@@ -114,13 +108,14 @@
       "${dep}",
   % endfor
     ]
-    configs -= [ "//build/config/compiler:chromium_code" ]
+  <% extra_configs = get_extra_configs(lib) %>
+  % if extra_configs:
     configs += [
-      "//build/config/compiler:no_chromium_code",
-  % for config in get_extra_configs(lib):
+  % for config in extra_configs:
       "${config}",
   % endfor
     ]
+  % endif
     public_configs = [
       ":grpc_config",
     ]
@@ -138,13 +133,14 @@
       "${dep}",
   % endfor
     ]
-    configs -= [ "//build/config/compiler:chromium_code" ]
+  <% extra_configs = get_extra_configs(tgt) %>
+  % if extra_configs:
     configs += [
-      "//build/config/compiler:no_chromium_code",
-  % for config in get_extra_configs(tgt):
+  % for config in extra_configs:
       "${config}",
   % endfor
     ]
+  % endif
     public_configs = [ ":grpc_config" ]
   }
   </%def>