add generic method comments to a few SDK methods

sdk/lib/math/math.dart

Index: sdk/lib/math/math.dart
diff --git a/sdk/lib/math/math.dart b/sdk/lib/math/math.dart
index d167d80f86a07823fbf6134be43ca104b04a090c..9182442863df32c0e739bf5d3077b6754672b254 100644
--- a/sdk/lib/math/math.dart
+++ b/sdk/lib/math/math.dart
@@ -63,7 +63,7 @@ const double SQRT2 = 1.4142135623730951;
   * same mathematical value) then it is unspecified which of the two arguments
   * is returned.
   */
-num min(num a, num b) {
+num/*=T*/ min/*<T extends num>*/(num/*=T*/ a, num/*=T*/ b) {
   // These partially redundant type checks improve code quality for dart2js.
   // Most of the improvement is at call sites from the inferred non-null num
   // return type.
@@ -98,7 +98,7 @@ num min(num a, num b) {
   * otherwise equal (including int and doubles with the same mathematical value)
   * then it is unspecified which of the two arguments is returned.
   */
-num max(num a, num b) {
+num/*=T*/ max/*<T extends num>*/(num/*=T*/ a, num/*=T*/ b) {
   // These partially redundant type checks improve code quality for dart2js.
   // Most of the improvement is at call sites from the inferred non-null num
   // return type.