Normalize path values and add additional error logging (fixes issue #2405)

This change also improves the settings documentation and enforces the
requirement that path values be absolute (see issue #2916).

include/internal/cef_types.h

@@ -170,23 +170,25 @@ typedef struct _cef_settings_t {
   // will be used. If this value is empty on macOS then a helper executable must
   // exist at "Contents/Frameworks/<app> Helper.app/Contents/MacOS/<app> Helper"
   // in the top-level app bundle. See the comments on CefExecuteProcess() for
-  // details. Also configurable using the "browser-subprocess-path" command-line
-  // switch.
+  // details. If this value is non-empty then it must be an absolute path. Also
+  // configurable using the "browser-subprocess-path" command-line switch.
   ///
   cef_string_t browser_subprocess_path;
 
   ///
   // The path to the CEF framework directory on macOS. If this value is empty
   // then the framework must exist at "Contents/Frameworks/Chromium Embedded
-  // Framework.framework" in the top-level app bundle. Also configurable using
-  // the "framework-dir-path" command-line switch.
+  // Framework.framework" in the top-level app bundle. If this value is
+  // non-empty then it must be an absolute path. Also configurable using the
+  // "framework-dir-path" command-line switch.
   ///
   cef_string_t framework_dir_path;
 
   ///
   // The path to the main bundle on macOS. If this value is empty then it
-  // defaults to the top-level app bundle. Also configurable using
-  // the "main-bundle-path" command-line switch.
+  // defaults to the top-level app bundle. If this value is non-empty then it
+  // must be an absolute path. Also configurable using the "main-bundle-path"
+  // command-line switch.
   ///
   cef_string_t main_bundle_path;
 
@@ -227,33 +229,35 @@ typedef struct _cef_settings_t {
 
   ///
   // The location where data for the global browser cache will be stored on
-  // disk. If non-empty this must be either equal to or a child directory of
-  // CefSettings.root_cache_path. If empty then browsers will be created in
-  // "incognito mode" where in-memory caches are used for storage and no data is
-  // persisted to disk. HTML5 databases such as localStorage will only persist
-  // across sessions if a cache path is specified. Can be overridden for
-  // individual CefRequestContext instances via the
-  // CefRequestContextSettings.cache_path value.
+  // disk. If this value is non-empty then it must be an absolute path that is
+  // either equal to or a child directory of CefSettings.root_cache_path. If
+  // this value is empty then browsers will be created in "incognito mode" where
+  // in-memory caches are used for storage and no data is persisted to disk.
+  // HTML5 databases such as localStorage will only persist across sessions if a
+  // cache path is specified. Can be overridden for individual CefRequestContext
+  // instances via the CefRequestContextSettings.cache_path value.
   ///
   cef_string_t cache_path;
 
   ///
   // The root directory that all CefSettings.cache_path and
   // CefRequestContextSettings.cache_path values must have in common. If this
-  // value is empty and CefSettings.cache_path is non-empty then this value will
-  // default to the CefSettings.cache_path value. Failure to set this value
-  // correctly may result in the sandbox blocking read/write access to the
-  // cache_path directory.
+  // value is empty and CefSettings.cache_path is non-empty then it will
+  // default to the CefSettings.cache_path value. If this value is non-empty
+  // then it must be an absolute path. Failure to set this value correctly may
+  // result in the sandbox blocking read/write access to the cache_path
+  // directory.
   ///
   cef_string_t root_cache_path;
 
   ///
   // The location where user data such as spell checking dictionary files will
-  // be stored on disk. If empty then the default platform-specific user data
-  // directory will be used ("~/.cef_user_data" directory on Linux,
-  // "~/Library/Application Support/CEF/User Data" directory on Mac OS X,
-  // "Local Settings\Application Data\CEF\User Data" directory under the user
-  // profile directory on Windows).
+  // be stored on disk. If this value is empty then the default
+  // platform-specific user data directory will be used ("~/.cef_user_data"
+  // directory on Linux, "~/Library/Application Support/CEF/User Data" directory
+  // on Mac OS X, "Local Settings\Application Data\CEF\User Data" directory
+  // under the user profile directory on Windows). If this value is non-empty
+  // then it must be an absolute path.
   ///
   cef_string_t user_data_path;
 
@@ -333,16 +337,17 @@ typedef struct _cef_settings_t {
   // The fully qualified path for the resources directory. If this value is
   // empty the cef.pak and/or devtools_resources.pak files must be located in
   // the module directory on Windows/Linux or the app bundle Resources directory
-  // on Mac OS X. Also configurable using the "resources-dir-path" command-line
-  // switch.
+  // on Mac OS X. If this value is non-empty then it must be an absolute path.
+  // Also configurable using the "resources-dir-path" command-line switch.
   ///
   cef_string_t resources_dir_path;
 
   ///
   // The fully qualified path for the locales directory. If this value is empty
-  // the locales directory must be located in the module directory. This value
-  // is ignored on Mac OS X where pack files are always loaded from the app
-  // bundle Resources directory. Also configurable using the "locales-dir-path"
+  // the locales directory must be located in the module directory. If this
+  // value is non-empty then it must be an absolute path. This value is ignored
+  // on Mac OS X where pack files are always loaded from the app bundle
+  // Resources directory. Also configurable using the "locales-dir-path"
   // command-line switch.
   ///
   cef_string_t locales_dir_path;
@@ -428,13 +433,13 @@ typedef struct _cef_request_context_settings_t {
 
   ///
   // The location where cache data for this request context will be stored on
-  // disk. If non-empty this must be either equal to or a child directory of
-  // CefSettings.root_cache_path. If empty then browsers will be created in
-  // "incognito mode" where in-memory caches are used for storage and no data is
-  // persisted to disk. HTML5 databases such as localStorage will only persist
-  // across sessions if a cache path is specified. To share the global browser
-  // cache and related configuration set this value to match the
-  // CefSettings.cache_path value.
+  // disk. If this value is non-empty then it must be an absolute path that is
+  // either equal to or a child directory of CefSettings.root_cache_path. If
+  // this value is empty then browsers will be created in "incognito mode" where
+  // in-memory caches are used for storage and no data is persisted to disk.
+  // HTML5 databases such as localStorage will only persist across sessions if a
+  // cache path is specified. To share the global browser cache and related
+  // configuration set this value to match the CefSettings.cache_path value.
   ///
   cef_string_t cache_path;