Add depot tools to the requirements section.

The depot_tools install was mentioned in the building section but was
missing from requirements. This CL fixes that oversight.

Bug: tint:35
Change-Id: I6900ba8916d26dc03bd001bde96561a468a2fb75
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/18900
Reviewed-by: Ryan Harrison <rharrison@chromium.org>
Commit-Queue: Ryan Harrison <rharrison@chromium.org>
diff --git a/README.md b/README.md
index f69ea92..86a0b50 100644
--- a/README.md
+++ b/README.md
@@ -9,6 +9,7 @@
  * CMake (3.10.2 or later)
  * Ninja (or other build tool)
  * Python, for fetching dependencies
+ * [depot_tools] in your path
 
 ## Build options
  * `TINT_BUILD_SPV_READER` : enable the SPIR-V input reader (off by default)
@@ -17,9 +18,10 @@
  * `TINT_BUILD_WGSL_WRITER` : enable the WGSL output writer (on by default)
 
 ## Building
-Tint uses Chromium dependency management so you need to [install depot_tools] and add it to your PATH.
+Tint uses Chromium dependency management so you need to install [depot_tools]
+and add it to your PATH.
 
-[install depot_tools]: http://commondatastorage.googleapis.com/chrome-infra-docs/flat/depot_tools/docs/html/depot_tools_tutorial.html#_setting_up
+[depot_tools]: http://commondatastorage.googleapis.com/chrome-infra-docs/flat/depot_tools/docs/html/depot_tools_tutorial.html#_setting_up
 
 ### Getting source & dependencies