gn: Fix some typos in unittests.

SubstitutionPatterm -> SubstitutionPattern
SubstutitionWriter -> SubstitutionWriter

BUG=None
TEST=ninja -C out/Debug gn_unittests - compare the output before and
after this change.
TBR=brettw@chromium.org

Review URL: https://codereview.chromium.org/590683002

Cr-Commit-Position: refs/heads/master@{#295846}

tools/gn/substitution_pattern_unittest.cc

@@ -16,7 +16,7 @@ TEST(SubstitutionPattern, ParseLiteral) {
   EXPECT_EQ("This is a literal", pattern.ranges()[0].literal);
 }
 
-TEST(SubstitutionPatterm, ParseComplex) {
+TEST(SubstitutionPattern, ParseComplex) {
   SubstitutionPattern pattern;
   Err err;
   EXPECT_TRUE(pattern.Parse(

tools/gn/substitution_writer_unittest.cc

@@ -59,7 +59,7 @@ TEST(SubstitutionWriter, ApplyPatternToSourceAsOutputFile) {
   ASSERT_EQ("gen/foo/bar/myfile.tmp", result.value());
 }
 
-TEST(SubstutitionWriter, WriteNinjaVariablesForSource) {
+TEST(SubstitutionWriter, WriteNinjaVariablesForSource) {
   TestWithScope setup;
 
   std::vector<SubstitutionType> types;
@@ -101,7 +101,7 @@ TEST(SubstitutionWriter, WriteWithNinjaVariables) {
       out.str());
 }
 
-TEST(SubstutitionWriter, SourceSubstitutions) {
+TEST(SubstitutionWriter, SourceSubstitutions) {
   TestWithScope setup;
 
   // Call to get substitutions relative to the build dir.