win: Set is_clang=true by default.

tools/mb/mb_config.pyl

Index: tools/mb/mb_config.pyl
diff --git a/tools/mb/mb_config.pyl b/tools/mb/mb_config.pyl
index 57e79d710b8059158bd58bdc7d2162a3f01a46df..737a45d1924ae148c4790403eb46b6b2e6d3d4e9 100644
--- a/tools/mb/mb_config.pyl
+++ b/tools/mb/mb_config.pyl
@@ -137,10 +137,11 @@
 
       # if CrWinClang is modified, please update CrWinClangGoma in the same way.
       'CrWinClang': 'clang_official_release_bot_minimal_symbols_x86',
-
       'CrWinClang(dbg)': 'clang_debug_bot_minimal_symbols_x86',
+      'CrWinClang(shared)': 'clang_minimal_symbols_shared_release_bot_x86',
       'CrWinClang64': 'clang_official_release_bot_minimal_symbols',
       'CrWinClang64(dll)': 'clang_shared_release_bot',
+      'CrWinClang64(dbg)': 'win_clang_debug_bot',
       'CrWinClangGoma': 'clang_official_optimize_release_bot_minimal_symbols_x86',
       'CrWinGoma': 'release_bot_x86',
       'CrWinGoma(dll)': 'shared_release_bot_x86',
@@ -170,8 +171,6 @@
       'CrWinAsan': 'asan_clang_fuzzer_static_v8_heap_x86_full_symbols_release',
       'CrWinAsan(dll)': 'asan_clang_shared_v8_heap_x86_full_symbols_release',
       'CrWinAsanCov': 'asan_clang_edge_fuzzer_static_v8_heap_x86_full_symbols_release',
-      'CrWinClang(shared)': 'clang_minimal_symbols_shared_release_bot_x86',
-      'CrWinClang64(dbg)': 'win_clang_debug_bot',
       'CrWinClangLLD': 'clang_tot_official_static_use_lld_x86',
       'CrWinClangLLD64': 'clang_tot_shared_release_use_lld',
       'CrWinClngLLD64dbg': 'clang_tot_full_symbols_shared_debug_use_lld',
@@ -1059,7 +1058,10 @@
     ],
 
     'clang_debug_bot_minimal_symbols_x86': [
-      'clang', 'debug_bot', 'minimal_symbols', 'x86',
+      # Now that the default win bots use clang, use a "clang" bot to make sure
+      # things stay compilable with msvc. TODO(thakis): Having a "clang" bot
+      # check that is very confusing, so rename the bot to "msvc".
+      'no_clang', 'debug_bot', 'minimal_symbols', 'x86',
     ],
 
     'clang_release_bot_minimal_symbols_x86': [
@@ -1067,15 +1069,24 @@
     ],
 
     'clang_minimal_symbols_shared_release_bot_x86': [
-      'clang', 'minimal_symbols', 'shared_release_bot', 'x86',
+      # Now that the default win bots use clang, use a "clang" bot to make sure
+      # things stay compilable with msvc. TODO(thakis): Having a "clang" bot
+      # check that is very confusing, so rename the bot to "msvc".
+      'no_clang', 'minimal_symbols', 'shared_release_bot', 'x86',
     ],
 
     'clang_official_release_bot_minimal_symbols': [
-      'clang', 'official', 'release_bot', 'minimal_symbols',
+      # Now that the default win bots use clang, use a "clang" bot to make sure
+      # things stay compilable with msvc. TODO(thakis): Having a "clang" bot
+      # check that is very confusing, so rename the bot to "msvc".
+      'no_clang', 'official', 'release_bot', 'minimal_symbols',
     ],
 
     'clang_official_release_bot_minimal_symbols_x86': [
-      'clang', 'official', 'release_bot', 'minimal_symbols', 'x86',
+      # Now that the default win bots use clang, use a "clang" bot to make sure
+      # things stay compilable with msvc. TODO(thakis): Having a "clang" bot
+      # check that is very confusing, so rename the bot to "msvc".
+      'no_clang', 'official', 'release_bot', 'minimal_symbols', 'x86',
     ],
 
     'clang_official_optimize_release_bot_minimal_symbols_x86': [
@@ -1091,7 +1102,10 @@
     ],
 
     'clang_shared_release_bot': [
-      'clang', 'shared_release_bot',
+      # Now that the default win bots use clang, use a "clang" bot to make sure
+      # things stay compilable with msvc. TODO(thakis): Having a "clang" bot
+      # check that is very confusing, so rename the bot to "msvc".
+      'no_clang', 'shared_release_bot',
     ],
 
     'clang_tot_asan_lsan_static_release': [
@@ -1500,7 +1514,10 @@
     ],
 
     'win_clang_debug_bot': [
-      'clang', 'debug_bot', 'minimal_symbols',
+      # Now that the default win bots use clang, use a "clang" bot to make sure
+      # things stay compilable with msvc. TODO(thakis): Having a "clang" bot
+      # check that is very confusing, so rename the bot to "msvc".
+      'no_clang', 'debug_bot', 'minimal_symbols',
     ],
 
     'windows_analyze': [
@@ -1590,11 +1607,11 @@
     },
 
     'chrome_pgo_phase_1': {
-      'gn_args': 'chrome_pgo_phase=1',
+      'gn_args': 'chrome_pgo_phase=1 is_clang=false',
     },
 
     'chrome_pgo_phase_2': {
-      'gn_args': 'chrome_pgo_phase=2',
+      'gn_args': 'chrome_pgo_phase=2 is_clang=false',
     },
 
     'chrome_with_codecs': {
@@ -1622,6 +1639,10 @@
       'gn_args': 'is_clang=true',
     },
 
+    'no_clang': {
+      'gn_args': 'is_clang=false',
+    },
+
     'cronet': {
       'gn_args': ('disable_file_support=true disable_ftp_support=true '
                   'enable_websockets=false use_platform_icu_alternatives=true '
@@ -1869,7 +1890,8 @@
     },
 
     'syzyasan': {
-      'gn_args': 'is_syzyasan=true',
+      # TODO(thakis): Figure out SyzyASan + clang story.
+      'gn_args': 'is_syzyasan=true is_clang=false',
     },
 
     'thin_lto': {