3 files changed, 44 insertions, 5 deletions
diff --git a/base/test/launcher/test_launcher.cc b/base/test/launcher/test_launcher.cc
index 0076634..1d0c8fe 100644
--- a/base/test/launcher/test_launcher.cc
+++ b/base/test/launcher/test_launcher.cc
@@ -552,14 +552,42 @@ bool TestLauncher::Init() {
     return false;
   }
 
-  if (!TakeInt32FromEnvironment(kTestTotalShards, &total_shards_))
-    return false;
-  if (!TakeInt32FromEnvironment(kTestShardIndex, &shard_index_))
-    return false;
+  // Initialize sharding. Command line takes precedence over legacy environment
+  // variables.
+  if (command_line->HasSwitch(switches::kTestLauncherTotalShards) &&
+      command_line->HasSwitch(switches::kTestLauncherShardIndex)) {
+    if (!StringToInt(
+            command_line->GetSwitchValueASCII(
+                switches::kTestLauncherTotalShards),
+            &total_shards_)) {
+      LOG(ERROR) << "Invalid value for " << switches::kTestLauncherTotalShards;
+      return false;
+    }
+    if (!StringToInt(
+            command_line->GetSwitchValueASCII(
+                switches::kTestLauncherShardIndex),
+            &shard_index_)) {
+      LOG(ERROR) << "Invalid value for " << switches::kTestLauncherShardIndex;
+      return false;
+    }
+    fprintf(stdout,
+            "Using sharding settings from command line. This is shard %d/%d\n",
+            shard_index_, total_shards_);
+    fflush(stdout);
+  } else {
+    if (!TakeInt32FromEnvironment(kTestTotalShards, &total_shards_))
+      return false;
+    if (!TakeInt32FromEnvironment(kTestShardIndex, &shard_index_))
+      return false;
+    fprintf(stdout,
+            "Using sharding settings from environment. This is shard %d/%d\n",
+            shard_index_, total_shards_);
+    fflush(stdout);
+  }
   if (shard_index_ < 0 ||
       total_shards_ < 0 ||
       shard_index_ >= total_shards_) {
-    LOG(ERROR) << "Invalid environment variables: we require 0 <= "
+    LOG(ERROR) << "Invalid sharding settings: we require 0 <= "
                << kTestShardIndex << " < " << kTestTotalShards
                << ", but you have " << kTestShardIndex << "=" << shard_index_
                << ", " << kTestTotalShards << "=" << total_shards_ << ".\n";
diff --git a/base/test/test_switches.cc b/base/test/test_switches.cc
index 18b4881..50b4513 100644
--- a/base/test/test_switches.cc
+++ b/base/test/test_switches.cc
@@ -26,6 +26,15 @@ const char switches::kTestLauncherSummaryOutput[] =
 const char switches::kTestLauncherPrintTestStdio[] =
     "test-launcher-print-test-stdio";
 
+// Index of the test shard to run, starting from 0 (first shard) to total shards
+// minus one (last shard).
+const char switches::kTestLauncherShardIndex[] =
+    "test-launcher-shard-index";
+
+// Total number of shards. Must be the same for all shards.
+const char switches::kTestLauncherTotalShards[] =
+    "test-launcher-total-shards";
+
 // Time (in milliseconds) that the tests should wait before timing out.
 const char switches::kTestLauncherTimeout[] = "test-launcher-timeout";
 // TODO(phajdan.jr): Clean up the switch names.
diff --git a/base/test/test_switches.h b/base/test/test_switches.h
index 330b925..a492058 100644
--- a/base/test/test_switches.h
+++ b/base/test/test_switches.h
@@ -15,6 +15,8 @@ extern const char kTestLauncherJobs[];
 extern const char kTestLauncherOutput[];
 extern const char kTestLauncherSummaryOutput[];
 extern const char kTestLauncherPrintTestStdio[];
+extern const char kTestLauncherShardIndex[];
+extern const char kTestLauncherTotalShards[];
 extern const char kTestLauncherTimeout[];
 extern const char kTestTinyTimeout[];
 extern const char kUiTestActionTimeout[];