Update to Chromium version 88.0.4324.0 (#827102)

- Mac: Xcode 12.2 and the MacOS 11.0 SDK are now required for building.
- MacOS 10.10 (Yosemite) is no longer supported (see https://crbug.com/1126056).
- Flash is no longer supported (see https://www.chromium.org/flash-roadmap).

cmake/cef_variables.cmake.in

@@ -311,7 +311,7 @@ if(OS_MAC)
 
   # Find the newest available base SDK.
   execute_process(COMMAND xcode-select --print-path OUTPUT_VARIABLE XCODE_PATH OUTPUT_STRIP_TRAILING_WHITESPACE)
-  foreach(OS_VERSION 10.15 10.14 10.13 10.12 10.11 10.10)
+  foreach(OS_VERSION 10.15 10.14 10.13 10.12 10.11)
     set(SDK "${XCODE_PATH}/Platforms/MacOSX.platform/Developer/SDKs/MacOSX${OS_VERSION}.sdk")
     if(NOT "${CMAKE_OSX_SYSROOT}" AND EXISTS "${SDK}" AND IS_DIRECTORY "${SDK}")
       set(CMAKE_OSX_SYSROOT ${SDK})
@@ -319,7 +319,7 @@ if(OS_MAC)
   endforeach()
 
   # Target SDK.
-  set(CEF_TARGET_SDK               "10.10")
+  set(CEF_TARGET_SDK               "10.11")
   list(APPEND CEF_COMPILER_FLAGS
     -mmacosx-version-min=${CEF_TARGET_SDK}
   )