Replace ASSERT(false) by RTC_NOTREACHED().

This cl was produced by

  git grep -l 'ASSERT(false)' |\
    xargs -n1 sed -i 's/ASSERT(false)/RTC_NOTREACHED()/'

followed by additional includes of base/checks.h in affected files,
git cl format to adjust spacing in webrtc/base/transformadapter.cc.
Finally, to make presubmit happy, one unnamed TODO marker was deleted
in that file.

This is a step towards deletion of base/common.h.

BUG=webrtc:6424

Review-Url: https://codereview.webrtc.org/2625003003
Cr-Original-Commit-Position: refs/heads/master@{#16009}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: c80e741ad0ab8348a45eddd451e95607689b6c22
diff --git a/api/webrtcsdp.cc b/api/webrtcsdp.cc
index 2c1ba64..dc701a4 100644
--- a/api/webrtcsdp.cc
+++ b/api/webrtcsdp.cc
@@ -23,6 +23,7 @@
 #include "webrtc/api/jsepicecandidate.h"
 #include "webrtc/api/jsepsessiondescription.h"
 #include "webrtc/base/arraysize.h"
+#include "webrtc/base/checks.h"
 #include "webrtc/base/common.h"
 #include "webrtc/base/logging.h"
 #include "webrtc/base/messagedigest.h"
@@ -664,7 +665,7 @@
   } else if (type == cricket::RELAY_PORT_TYPE) {
     preference = kPreferenceRelayed;
   } else {
-    ASSERT(false);
+    RTC_NOTREACHED();
   }
   return preference;
 }
@@ -1241,7 +1242,7 @@
   else if (media_type == cricket::MEDIA_TYPE_DATA)
     type = kMediaTypeData;
   else
-    ASSERT(false);
+    RTC_NOTREACHED();
 
   std::string fmt;
   if (media_type == cricket::MEDIA_TYPE_VIDEO) {
@@ -1830,7 +1831,7 @@
       type = kCandidatePrflx;
       // Peer reflexive candidate may be signaled for being removed.
     } else {
-      ASSERT(false);
+      RTC_NOTREACHED();
       // Never write out candidates if we don't know the type.
       continue;
     }
@@ -2249,7 +2250,7 @@
       *content_name = cricket::CN_DATA;
       break;
     default:
-      ASSERT(false);
+      RTC_NOTREACHED();
       break;
   }
   if (!ParseContent(message, media_type, mline_index, protocol, payload_types,