Make merging of shard test results handle test suites that are split across shards better.

tools/sharding_supervisor/gtest_results.xml0

Index: tools/sharding_supervisor/gtest_results.xml0
diff --git a/tools/sharding_supervisor/gtest_results.xml0 b/tools/sharding_supervisor/gtest_results.xml0
new file mode 100644
index 0000000000000000000000000000000000000000..f6bf83a89c0db5ac2a4dd79b3f3bcd82a5a25327
--- /dev/null
+++ b/tools/sharding_supervisor/gtest_results.xml0
@@ -0,0 +1,23 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<testsuites name="AllTests" tests="" failures="" disabled="" errors="" time="">
+  <!-- Suite that is run entirely on shard 0 -->
+  <testsuite name="Suite0" tests="1" failures="" disabled="" errors="" time="">
+    <testcase name="Test0" status="run" time="0" classname="Suite0" />
+  </testsuite>
+
+  <!-- Suite that is run entirely on shard 1 -->
+  <testsuite name="Suite1" tests="1" failures="" disabled="" errors="" time="">
+  </testsuite>
+
+  <!-- Suite that has tests run on both shard 0 and shard 1 -->
+  <testsuite name="Suite2" tests="2" failures="" disabled="" errors="" time="">
+    <testcase name="Test0" status="run" time="0" classname="Suite2" />
+  </testsuite>
+
+  <!-- Suite that has a test run on both shard 0 and shard 1 -->
+  <testsuite name="Suite3" tests="1" failures="" disabled="" errors="" time="">
+    <testcase name="Test0" status="run" time="0" classname="Suite3">
+      <failure message="" type="" ignored="true"></failure>
+    </testcase>
+  </testsuite>
+</testsuites>