Add gn target for running sizes.py against //chrome.

Bug: 961548
Change-Id: I7638bd524d1802bdc9bc02ddd7437a9d395e2240
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1604184Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Commit-Queue: John Budorick <jbudorick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#658578}

chrome/test/BUILD.gn

@@ -2395,6 +2395,8 @@ test("browser_tests") {
 }
 
 if (is_linux || is_mac || is_win) {
+  import("//tools/binary_size/sizes.gni")
+
   group("browser_tests_apprtc") {
     testonly = true
     data_deps = [
@@ -2411,6 +2413,12 @@ if (is_linux || is_mac || is_win) {
       write_runtime_deps = "$root_out_dir/$target_name.runtime_deps"
     }
   }
+
+  sizes_test("chrome_sizes") {
+    data_deps = [
+      "//chrome",
+    ]
+  }
 }
 
 group("telemetry_perf_unittests") {