build: define V8_CONTIGUOUS_COMPRESSED_RO_SPACE for shared cage

Since the V8 14.2 update, `globals.h` sizes the read-only space
reservation in the shared pointer compression cage from
`V8_CONTIGUOUS_COMPRESSED_RO_SPACE_SIZE_MB`, which BUILD.gn defines
together with `V8_CONTIGUOUS_COMPRESSED_RO_SPACE` whenever
`v8_enable_pointer_compression_shared_cage` is set. features.gypi
defines neither, so builds configured with
`--experimental-pointer-compression-shared-cage` fail to compile V8.
Define both the way BUILD.gn does, with the same 16 MB default.

Refs: #60254
Signed-off-by: Shelley Vohr <shelley.vohr@gmail.com>
PR-URL: #65464
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Filip Skokan <panva.ip@gmail.com>

Author: codebytere

tools/v8_gypfiles/features.gypi

@@ -161,6 +161,9 @@
     'v8_enable_pointer_compression_shared_cage%': 0,
     'v8_enable_31bit_smis_on_64bit_arch%': 0,
 
+    # Size of the contiguous read-only space reservation in the shared cage.
+    'v8_contiguous_compressed_ro_space_size_mb%': 16,
+
     # Sets -dV8_SHORT_BUILTIN_CALLS
     'v8_enable_short_builtin_calls%': 0,
 
@@ -365,7 +368,11 @@
         'defines': ['V8_COMPRESS_POINTERS_IN_MULTIPLE_CAGES'],
       }],
       ['v8_enable_pointer_compression_shared_cage==1', {
-        'defines': ['V8_COMPRESS_POINTERS_IN_SHARED_CAGE'],
+        'defines': [
+          'V8_COMPRESS_POINTERS_IN_SHARED_CAGE',
+          'V8_CONTIGUOUS_COMPRESSED_RO_SPACE',
+          'V8_CONTIGUOUS_COMPRESSED_RO_SPACE_SIZE_MB=<(v8_contiguous_compressed_ro_space_size_mb)',
+        ],
       }],
       ['v8_enable_pointer_compression==1 or v8_enable_31bit_smis_on_64bit_arch==1', {
         'defines': ['V8_31BIT_SMIS_ON_64BIT_ARCH',],