Add warnings not to use "is_component_build=true" when using

use_clang_coverage.


Bug: 773530
Change-Id: I7d9002279230b6aa6efaf9cf5ed09117ae4e6ff0
Reviewed-on: https://chromium-review.googlesource.com/711217
Reviewed-by: Max Moroz <mmoroz@chromium.org>
Commit-Queue: Max Moroz <mmoroz@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#507983}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: cc786b3eb32eb1e4c9b844fce74d3e6f5ee1b4b9

config/coverage/coverage.gni

@@ -5,7 +5,11 @@
 import("//build/toolchain/toolchain.gni")
 
 declare_args() {
-  # Enable Clang's Source-based Code Coverage.
+  # Enable Clang's Source-based Code Coverage. This should not be used with
+  # is_component_build=true.
+  # TODO(metzman): Add an assertion that will prevent is_component_build=true
+  # from being passed as an argument to gn, but will not force toolchains that
+  # set is_component_build=true to set it to false.
   use_clang_coverage = false
 }