Update URL for GN quick start guide.

Change-Id: I8c76cf49161daf8cccaa1cfc32db8fcd930f01da
Reviewed-on: https://chromium-review.googlesource.com/1178692
Reviewed-by: Dirk Pranke <[email protected]>
Commit-Queue: Dirk Pranke <[email protected]>
Cr-Commit-Position: refs/heads/master@{#583909}
diff --git a/docs/windows_build_instructions.md b/docs/windows_build_instructions.md
index b6cf310..dbf874fb 100644
--- a/docs/windows_build_instructions.md
+++ b/docs/windows_build_instructions.md
@@ -138,10 +138,10 @@
 
 ## Setting up the build
 
-Chromium uses [Ninja](https://ninja-build.org) as its main build tool along
-with a tool called [GN](../tools/gn/docs/quick_start.md) to generate `.ninja`
-files. You can create any number of *build directories* with different
-configurations. To create a build directory:
+Chromium uses [Ninja](https://ninja-build.org) as its main build tool along with
+a tool called [GN](https://gn.googlesource.com/gn/+/master/docs/quick_start.md)
+to generate `.ninja` files. You can create any number of *build directories*
+with different configurations. To create a build directory:
 
 ```shell
 $ gn gen out/Default
@@ -155,8 +155,8 @@
   configuration](https://www.chromium.org/developers/gn-build-configuration).
   The default will be a debug component build matching the current host
   operating system and CPU.
-* For more info on GN, run `gn help` on the command line or read the
-  [quick start guide](../tools/gn/docs/quick_start.md).
+* For more info on GN, run `gn help` on the command line or read the [quick
+  start guide](https://gn.googlesource.com/gn/+/master/docs/quick_start.md).
 
 ### Using the Visual Studio IDE