Add notice of mirror deprecation.

This CL adds notice of the Tint mirror deprecation.

Bug: 344642397
Change-Id: I3c13d2eac8e47a115f8685ef0464295fe38ec3c4
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/194163
Kokoro: David Neto <dneto@google.com>
Commit-Queue: David Neto <dneto@google.com>
Reviewed-by: James Price <jrprice@google.com>
Kokoro: dan sinclair <dsinclair@chromium.org>
Auto-Submit: dan sinclair <dsinclair@chromium.org>
Reviewed-by: David Neto <dneto@google.com>
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1930b90..25ac7f7 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -26,6 +26,8 @@
   set(CMAKE_BUILD_TYPE "Debug")
 endif()
 
+message(WARNING "Note: https://dawn.googlesource.com/tint is deprecated and the auto-mirroring has been turned off. No more updates will appear in this mirror. Please switch to the Dawn repo (https://dawn.googlesource.com/dawn) to retrieve the Tint source code. If there are any issues integrating the Dawn repo with your build, please file bugs at (https://crbug.com/dawn).")
+
 set(DAWN_BUILD_GEN_DIR "${CMAKE_CURRENT_BINARY_DIR}/gen")
 
 # TINT_IS_SUBPROJECT is 1 if added via add_subdirectory() from another project.
diff --git a/README.md b/README.md
index 58f05aa..7b3efae 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,12 @@
 # Tint
 
 ---
+Note: This repo is deprecated and the auto-mirroring has been turned
+off. No more updates will appear in this mirror. Please switch to
+[the Dawn repo](https://dawn.googlesource.com/dawn) to retrieve the Tint
+source code. If there are any issues integrating the Dawn repo with your
+build, please [file bugs](https://crbug.com/dawn).
+
 Note: This repo is read-only, minimized mirror of [the Dawn repo](https://dawn.googlesource.com/dawn).
 
 **Tint changes should be made in [the Dawn repo](https://dawn.googlesource.com/dawn).**