Bug 1366860 - Require a minimum amount of RAM to get a 64-bit build from the stub installer. r=rstrong

MozReview-Commit-ID: 4lR9pjafnTq

--HG--
extra : rebase_source : 37dbab58bce96d2697ede973b44b81c00a6fef75

browser/installer/windows/nsis/stub.nsi

@@ -181,6 +181,14 @@ Var PreviousInstallArch
 !define BlurbDisplayMS 19500
 !define BlurbBlankMS 500
 
+; Amount of physical memory required for the 64-bit build to be selected.
+; Machines with less RAM than this get the 32-bit build, even with a 64-bit OS.
+; The value 1800 MB was chosen based on an initial requirement of 2 GB, reduced
+; to allow for hardware such as integrated graphics that reserves some of the
+; installed RAM for its own use.
+; 1800 MB * 1024 KB/MB * 1024 B/KB = 1887436800 bytes
+!define RAM_NEEDED_FOR_64BIT 1887436800
+
 ; Attempt to elevate Standard Users in addition to users that
 ; are a member of the Administrators group.
 !define NONADMIN_ELEVATE
@@ -312,9 +320,18 @@ Function .onInit
     Quit
   ${EndIf}
 
+  ; Check if we meet the RAM requirement for the 64-bit build.
+  System::Call "*(i 64, i, l 0, l, l, l, l, l, l)p.r0"
+  System::Call "Kernel32::GlobalMemoryStatusEx(p r0)"
+  System::Call "*$0(i, i, l.r1, l, l, l, l, l, l)"
+  System::Free $0
+
   ${If} ${RunningX64}
+  ${AndIf} $1 L>= ${RAM_NEEDED_FOR_64BIT}
+    StrCpy $DroplistArch "$(VERSION_64BIT)"
     StrCpy $INSTDIR "${DefaultInstDir64bit}"
   ${Else}
+    StrCpy $DroplistArch "$(VERSION_32BIT)"
     StrCpy $INSTDIR "${DefaultInstDir32bit}"
   ${EndIf}
 
@@ -423,11 +440,6 @@ Function .onInit
 !else
   StrCpy $CheckboxInstallMaintSvc "0"
 !endif
-  ${If} ${RunningX64}
-    StrCpy $DroplistArch "$(VERSION_64BIT)"
-  ${Else}
-    StrCpy $DroplistArch "$(VERSION_32BIT)"
-  ${EndIf}
 
   StrCpy $0 ""
 !ifdef FONT_FILE1