Add install-protobuf.sh and make .travis.yml always test proto for te…

…sting this PR

.travis.yml

@@ -10,10 +10,10 @@ go_import_path: google.golang.org/grpc
 before_install:
   - if [[ $TRAVIS_GO_VERSION = 1.8* ]]; then go get -u github.com/golang/lint/golint honnef.co/go/tools/cmd/staticcheck; fi
   - go get -u golang.org/x/tools/cmd/goimports github.com/axw/gocov/gocov github.com/mattn/goveralls golang.org/x/tools/cmd/cover
-  - if [[ "$TRAVIS_EVENT_TYPE" = cron ]]; then PROTOBUF_VERSION=3.3.0 ./install-protobuf.sh && PATH=/home/travis/bin:$PATH protoc --version; fi
+  - PROTOBUF_VERSION=3.3.0 ./install-protobuf.sh
 
 script:
-  - 'if [[ "$TRAVIS_EVENT_TYPE" = cron ]]; then PATH=/home/travis/bin:$PATH make proto && ! git status --porcelain | tee /dev/stderr | read || (git status; git diff; exit 1); fi'
+  - 'PATH=/home/travis/bin:$PATH make proto && ! git status --porcelain | tee /dev/stderr | read || (git status; git diff; exit 1)'
   - 'set -o pipefail && git ls-files "*.go" | xargs grep -L "\(Copyright [0-9]\{4,\} gRPC authors\)\|DO NOT EDIT" 2>&1 | tee /dev/stderr | (! read)'
   - 'set -o pipefail && gofmt -s -d -l . 2>&1 | tee /dev/stderr | (! read)'
   - 'set -o pipefail && goimports -l . 2>&1 | tee /dev/stderr | (! read)'

Makefile

@@ -20,7 +20,7 @@ proto:
 		echo "error: protoc not installed" >&2; \
 		exit 1; \
 	fi
-	go get -u -v github.com/golang/protobuf/protoc-gen-go
+	go get -u -v github.com/golang/protobuf/protoc-gen-go golang.org/x/tools/cmd/stringer
 	go generate google.golang.org/grpc/...
 
 test: testdeps

install-protobuf.sh

@@ -0,0 +1,23 @@
+#!/usr/bin/env bash
+
+set -ex
+
+die() {
+    echo "$@" >&2
+    exit 1
+}
+
+case "$PROTOBUF_VERSION" in
+3*)
+    basename=protoc-$PROTOBUF_VERSION
+    ;;
+*)
+    die "unknown protobuf version: $PROTOBUF_VERSION"
+    ;;
+esac
+
+cd /home/travis
+
+wget https://github.com/google/protobuf/releases/download/v$PROTOBUF_VERSION/$basename-linux-x86_64.zip
+unzip $basename-linux-x86_64.zip
+bin/protoc --version