all: be more idiomatic when documenting boolean return values.

Phrases like "returns whether or not the image is opaque" could be
describing what the function does (it always returns, regardless of
the opacity) or what it returns (a boolean indicating the opacity).
Even when the "or not" is missing, the phrasing is bizarre.

Go with "reports whether", which is still clunky but at least makes
it clear we're talking about the return value.

R=golang-dev, dsymonds
CC=golang-dev
https://golang.org/cl/11458046

cmd/cover/html.go

@@ -275,7 +275,7 @@ func htmlGen(w io.Writer, src []byte, tokens []Token) error {
 }
 
 // startBrowser tries to open the URL in a browser
-// and returns whether it succeed.
+// and reports whether it succeeds.
 func startBrowser(url string) bool {
 	// try to start the browser
 	var args []string

godoc/util/util.go

@@ -35,7 +35,7 @@ func (v *RWValue) Get() (interface{}, time.Time) {
 	return v.value, v.timestamp
 }
 
-// IsText returns whether a significant prefix of s looks like correct UTF-8;
+// IsText reports whether a significant prefix of s looks like correct UTF-8;
 // that is, if it is likely that s is human-readable text.
 func IsText(s []byte) bool {
 	const max = 1024 // at least utf8.UTFMax
@@ -61,7 +61,7 @@ var textExt = map[string]bool{
 	".js":  false, // must be served raw
 }
 
-// IsTextFile returns whether the file has a known extension indicating
+// IsTextFile reports whether the file has a known extension indicating
 // a text file, or if a significant chunk of the specified file looks like
 // correct UTF-8; that is, if it is likely that the file contains human-
 // readable text.