Verify that gin_shell and hello_world.js exist.

gin/shell/gin_shell_unittest.cc

Index: gin/shell/gin_shell_unittest.cc
diff --git a/gin/shell/gin_shell_unittest.cc b/gin/shell/gin_shell_unittest.cc
index 0df979de71b6d5ef7286d94809b0d41a7e777c56..f80d6b0c3c290958bc400a9115f407e019c093d4 100644
--- a/gin/shell/gin_shell_unittest.cc
+++ b/gin/shell/gin_shell_unittest.cc
@@ -3,7 +3,7 @@
 // found in the LICENSE file.
 
 #include "base/command_line.h"
-#include "base/files/file_path.h"
+#include "base/file_util.h"
 #include "base/path_service.h"
 #include "base/process/launch.h"
 #include "base/strings/string_util.h"
@@ -25,8 +25,13 @@ base::FilePath HelloWorldPath() {
 }
 
 TEST(GinShellTest, HelloWorld) {
-  CommandLine cmd(GinShellPath());
-  cmd.AppendArgPath(HelloWorldPath());
+  base::FilePath gin_shell_path(GinShellPath());
+  base::FilePath hello_world_path(HelloWorldPath());
+  ASSERT_TRUE(base::PathExists(gin_shell_path));
+  ASSERT_TRUE(base::PathExists(hello_world_path));
+
+  CommandLine cmd(gin_shell_path);
+  cmd.AppendArgPath(hello_world_path);
   std::string output;
   ASSERT_TRUE(base::GetAppOutput(cmd, &output));
   base::TrimWhitespaceASCII(output, base::TRIM_ALL, &output);