Java: Add approx contents.

Author: aschackmull

java/ql/lib/semmle/code/java/dataflow/internal/DataFlowNodes.qll

@@ -81,7 +81,9 @@ private module Cached {
     TMapKeyContentApprox() or
     TMapValueContentApprox() or
     TCapturedVariableContentApprox(CapturedVariable v) or
-    TSyntheticFieldApproxContent()
+    TSyntheticFieldApproxContent() or
+    TLambdaReturnApprox(Method m) or
+    TLambdaArgumentApprox(Method m, ArgumentPosition pos)
 }
 
 import Cached

java/ql/lib/semmle/code/java/dataflow/internal/DataFlowPrivate.qll

@@ -774,6 +774,13 @@ ContentApprox getContentApprox(Content c) {
   )
   or
   c instanceof SyntheticFieldContent and result = TSyntheticFieldApproxContent()
+  or
+  exists(Method m |
+    c = TLambdaReturn(m) and result = TLambdaReturnApprox(m))
+  or
+  exists(Method m, ArgumentPosition pos |
+    c = TLambdaArgument(m, pos) and result = TLambdaArgumentApprox(m, pos))
+
 }
 
 /**