Add Log.h to replace all uses of iostream

On Android iostream doesn't appear in logcat, the system log that's
often used for printf debugging. Introduce Chromium/ANGLE like logging
that looks like the following:

  InfoLog() << stuff << stuff;

This makes sure the message is put in logcat on Android and removes
static initializers from <iostream>

BUG=dawn:286

Change-Id: Ie0d018f49bcac1a7b740739a6e59d45ae6728638
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/14102
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: David Turner <digit@google.com>
Reviewed-by: Austin Eng <enga@chromium.org>

src/tests/perf_tests/DawnPerfTest.cpp

@@ -15,6 +15,7 @@
 #include "tests/perf_tests/DawnPerfTest.h"
 
 #include "common/Assert.h"
+#include "common/Log.h"
 #include "dawn_platform/tracing/TraceEvent.h"
 #include "tests/perf_tests/DawnPerfTestPlatform.h"
 #include "utils/Timer.h"
@@ -112,14 +113,13 @@ DawnPerfTestEnvironment::DawnPerfTestEnvironment(int argc, char** argv)
         }
 
         if (strcmp("-h", argv[i]) == 0 || strcmp("--help", argv[i]) == 0) {
-            std::cout
+            InfoLog()
                 << "Additional flags:"
                 << " [--calibration] [--override-steps=x] [--enable-tracing] [--trace-file=file]\n"
                 << "  --calibration: Only run calibration. Calibration allows the perf test"
                    " runner script to save some time.\n"
                 << " --override-steps: Set a fixed number of steps to run for each test\n"
-                << " --trace-file: The file to dump trace results.\n"
-                << std::endl;
+                << " --trace-file: The file to dump trace results.\n";
             continue;
         }
     }