[Qt][WK2] Compute and set cache capacities using the current CacheModel

[Qt][WK2] Compute and set cache capacities using the current CacheModel
https://bugs.webkit.org/show_bug.cgi?id=73918

Patch by Michael Brüning <michael.bruning@nokia.com> on 2012-02-07
Reviewed by Kenneth Rohde Christiansen.

Source/WebCore:

No new tests. (Not applicable)

Added OS-specific implementation for retrieving the free disk space.

* platform/FileSystem.h:
(WebCore):
* platform/qt/FileSystemQt.cpp:
(WebCore::getVolumeFreeSizeForPath):
(WebCore):

Source/WebKit2:

First part of the implementation. The next steps are the implementation
of the API for the Qt WebKit 2 port and the hybrid memory and disk cache.

* Shared/WebProcessCreationParameters.cpp:
(WebKit::WebProcessCreationParameters::encode):
(WebKit::WebProcessCreationParameters::decode):
* Shared/WebProcessCreationParameters.h:
(WebProcessCreationParameters):
* UIProcess/qt/WebContextQt.cpp:
(WebKit::defaultDiskCacheDirectory):
(WebKit):
(WebKit::WebContext::platformInitializeWebProcess):
* WebProcess/qt/WebProcessQt.cpp:
(WebKit::physicalMemorySizeInBytes):
(WebKit):
(WebKit::WebProcess::platformSetCacheModel):
(WebKit::WebProcess::platformInitializeWebProcess):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@106920 268f45cc-cd09-0410-ab3c-d52691b4dbfc