Fix google3 license related issues

Append BSD license to LICENSE.

Change-Id: Ie6688396bc06cdf4e34add729134454054dd4b31
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/71442
Reviewed-by: Ben Clayton <bclayton@google.com>
Commit-Queue: Shrek Shao <shrekshao@google.com>

LICENSE

@@ -200,3 +200,36 @@
     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     See the License for the specific language governing permissions and
     limitations under the License.
+
+----------
+The following license is exclusively used by the template generated header files.
+
+BSD 3-Clause License
+
+Copyright (c) 2019, "WebGPU native" developers
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+1. Redistributions of source code must retain the above copyright notice, this
+   list of conditions and the following disclaimer.
+
+2. Redistributions in binary form must reproduce the above copyright notice,
+   this list of conditions and the following disclaimer in the documentation
+   and/or other materials provided with the distribution.
+
+3. Neither the name of the copyright holder nor the names of its
+   contributors may be used to endorse or promote products derived from
+   this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

dawn.json

@@ -20,7 +20,8 @@
     "_metadata": {
         "api": "WebGPU",
         "c_prefix": "WGPU",
-        "namespace": "wgpu"
+        "namespace": "wgpu",
+        "copyright_year": "2019"
     },
 
     "create instance": {

generator/templates/api.h

@@ -21,8 +21,7 @@
 //*
 // BSD 3-Clause License
 //
-{% set year = metadata.copyright_year if metadata.copyright_year else 2019 %}
-// Copyright (c) {{year}}, "{{metadata.api}} native" developers
+// Copyright (c) {{metadata.copyright_year}}, "{{metadata.api}} native" developers
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without