cmd/go: add support for -test.benchmem

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/6587074

src/cmd/go/test.go

@@ -94,6 +94,9 @@ directory containing the package sources, has its own flags:
 	    Run benchmarks matching the regular expression.
 	    By default, no benchmarks run.
 
+	-test.benchmem
+	    Print memory allocation statistics for benchmarks.
+
 	-test.cpuprofile cpu.out
 	    Write a CPU profile to the specified file before exiting.
 

src/cmd/go/testflag.go

@@ -25,6 +25,7 @@ var usageMessage = `Usage of go test:
 
   // These flags can be passed with or without a "test." prefix: -v or -test.v.
   -bench="": passes -test.bench to test
+  -benchmem=false: print memory allocation statistics for benchmarks
   -benchtime=1: passes -test.benchtime to test
   -cpu="": passes -test.cpu to test
   -cpuprofile="": passes -test.cpuprofile to test
@@ -75,6 +76,7 @@ var testFlagDefn = []*testFlagSpec{
 
 	// passed to 6.out, adding a "test." prefix to the name if necessary: -v becomes -test.v.
 	{name: "bench", passToTest: true},
+	{name: "benchmem", boolVar: new(bool), passToTest: true},
 	{name: "benchtime", passToTest: true},
 	{name: "cpu", passToTest: true},
 	{name: "cpuprofile", passToTest: true},