[Jumbo] Add support for jumbo compilation in components/metrics

The code in components/metrics takes about >3CPU minutes to build.
Building effort will fall to about 1 CPU minutes using jumbo builds[1].
When building using jumbo, files gets merged.
It means that you cannot duplicate symbol names within the component,
not even in anonymous namespaces.

[1] https://chromium.googlesource.com/chromium/src/+/lkgr/docs/jumbo.md

Bug: 869381
Change-Id: I5287f8366ea78b6e97c51d04489ec3c2ed28fab6
Reviewed-on: https://chromium-review.googlesource.com/1239133
Commit-Queue: Byoungkwon Ko <codeimpl@gmail.com>
Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#595473}

components/metrics/BUILD.gn

@@ -2,9 +2,10 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import("//build/config/jumbo.gni")
 import("//testing/test.gni")
 
-static_library("metrics") {
+jumbo_static_library("metrics") {
   sources = [
     "call_stack_profile_metrics_provider.cc",
     "call_stack_profile_metrics_provider.h",
@@ -181,7 +182,7 @@ if (!is_ios) {
   }
 }
 
-static_library("net") {
+jumbo_static_library("net") {
   sources = [
     "net/cellular_logic_helper.cc",
     "net/cellular_logic_helper.h",
@@ -321,7 +322,7 @@ source_set("call_stack_profile_collector") {
   ]
 }
 
-static_library("test_support") {
+jumbo_static_library("test_support") {
   testonly = true
   sources = [
     "test_enabled_state_provider.cc",