Build out backoff as a library
diff --git a/tools/run_tests/sources_and_headers.json b/tools/run_tests/sources_and_headers.json
index 0c7a6c7..d547ca6 100644
--- a/tools/run_tests/sources_and_headers.json
+++ b/tools/run_tests/sources_and_headers.json
@@ -379,6 +379,20 @@
     ], 
     "headers": [], 
     "language": "c", 
+    "name": "gpr_backoff_test", 
+    "src": [
+      "test/core/support/backoff_test.c"
+    ], 
+    "third_party": false, 
+    "type": "target"
+  }, 
+  {
+    "deps": [
+      "gpr", 
+      "gpr_test_util"
+    ], 
+    "headers": [], 
+    "language": "c", 
     "name": "gpr_cmdline_test", 
     "src": [
       "test/core/support/cmdline_test.c"
@@ -3706,6 +3720,7 @@
       "include/grpc/support/tls_pthread.h", 
       "include/grpc/support/useful.h", 
       "src/core/profiling/timers.h", 
+      "src/core/support/backoff.h", 
       "src/core/support/block_annotate.h", 
       "src/core/support/env.h", 
       "src/core/support/load_file.h", 
@@ -3767,6 +3782,8 @@
       "src/core/profiling/timers.h", 
       "src/core/support/alloc.c", 
       "src/core/support/avl.c", 
+      "src/core/support/backoff.c", 
+      "src/core/support/backoff.h", 
       "src/core/support/block_annotate.h", 
       "src/core/support/cmdline.c", 
       "src/core/support/cpu_iphone.c",