Update component build documentation.

build/config/BUILDCONFIG.gn

 # Copyright (c) 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # =============================================================================
 # PLATFORM SELECTION
 # =============================================================================
 #
 # There are two main things to set: "os" and "cpu". The "toolchain" is the name
 # of the GN thing that encodes combinations of these things.
@@ skipping 126 matching lines @@
   # every toolchain can pass through the "global" value via toolchain_args().
   host_toolchain = ""
 
   # DON'T ADD MORE FLAGS HERE. Read the comment above.
 }
 
 declare_args() {
   # Component build. Setting to true compiles targets declared as "components"
   # as shared libraries loaded dynamically. This speeds up development time.
   # When false, components will be linked statically.
+  #
+  # For more information see
+  # https://chromium.googlesource.com/chromium/src/+/master/docs/component_build.md

[Dirk Pranke, 2016/08/04 15:59:04]

I'm tempted to say that this should be "//docs/component_build.md" or
"../../docs/component_build.md" instead, but neither of those gives you a
clickable link, so I'm not really sure they're improvements.

[brettw, 2016/08/04 18:26:41]

I considered that, but decided most people will prefer to read on the web than
in raw markdown form.

   is_component_build = is_debug && current_os != "ios"
 }
 
 assert(!(is_debug && is_official_build), "Can't do official debug builds")
 
 # ==============================================================================
 # TOOLCHAIN SETUP
 # ==============================================================================
 #
 # Here we set the default toolchain, as well as the variable host_toolchain
@@ skipping 467 matching lines @@
 set_defaults("component") {
   if (is_component_build) {
     configs = default_shared_library_configs
     if (is_android) {
       configs -= [ "//build/config/android:hide_native_jni_exports" ]
     }
   } else {
     configs = default_compiler_configs
   }
 }