Add ANGLE platform methods for boolean histograms.

ui/gl/angle_platform_impl.cc

Index: ui/gl/angle_platform_impl.cc
diff --git a/ui/gl/angle_platform_impl.cc b/ui/gl/angle_platform_impl.cc
index 732f0882ac76258c5479f52d343690539c4283b9..5ad8b51d54436259377f70390252bf9d49ec3906 100644
--- a/ui/gl/angle_platform_impl.cc
+++ b/ui/gl/angle_platform_impl.cc
@@ -95,4 +95,8 @@ void ANGLEPlatformImpl::histogramSparse(const char* name, int sample) {
   UMA_HISTOGRAM_SPARSE_SLOWLY(name, sample);
 }
 
+void ANGLEPlatformImpl::histogramBoolean(const char* name, bool sample) {
+  histogramEnumeration(name, sample ? 1 : 0, 2);
+}
+
 }  // namespace gfx